💄

find_test.go

@@ -1,7 +1,7 @@
 package lo
 
 import (
-	"fmt"
+	"errors"
 	"math/rand"
 	"testing"
 	"time"
@@ -374,9 +374,12 @@ func TestMinByErr(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
-			result, err := MinByErr(tt.input, func(item, min string) (bool, error) {
-				return len(item) < len(min), nil
+			t.Parallel()
+
+			result, err := MinByErr(tt.input, func(item, mIn string) (bool, error) {
+				return len(item) < len(mIn), nil
 			})
 			is.NoError(err)
 			is.Equal(tt.expected, result)
@@ -405,23 +408,21 @@ func TestMinByErr(t *testing.T) {
 	}
 
 	for _, tt := range errorTests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			callbackCount := 0
-			result, err := MinByErr(tt.input, func(item, min string) (bool, error) {
+			result, err := MinByErr(tt.input, func(item, mIn string) (bool, error) {
 				callbackCount++
 				if item == tt.errorAt {
 					return false, testErr
 				}
-				return len(item) < len(min), nil
+				return len(item) < len(mIn), nil
 			})
 			is.ErrorIs(err, testErr)
 			is.Equal(tt.expectedCalls, callbackCount)
-			// Result should be the current min at the time of error
-			if tt.expectedCalls == 1 {
-				is.Equal("a", result) // Still the first element
-			} else {
-				is.Equal("a", result) // "a" is still min
-			}
+			is.Equal("a", result) // Still the first element
 		})
 	}
 }
@@ -454,43 +455,43 @@ func TestMinIndexByErr(t *testing.T) {
 	t.Parallel()
 
 	tests := []struct {
-		name                 string
-		input                []string
-		less                 func(a, b string) (bool, error)
-		wantValue            string
-		wantIndex            int
-		wantErr              bool
-		errMsg               string
+		name                  string
+		input                 []string
+		less                  func(a, b string) (bool, error)
+		wantValue             string
+		wantIndex             int
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
-			name:     "empty slice",
-			input:    []string{},
-			less:     func(a, b string) (bool, error) { return len(a) < len(b), nil },
-			wantValue: "",
-			wantIndex: -1,
-			wantErr:              false,
+			name:                  "empty slice",
+			input:                 []string{},
+			less:                  func(a, b string) (bool, error) { return len(a) < len(b), nil },
+			wantValue:             "",
+			wantIndex:             -1,
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
-			name:     "success case",
-			input:    []string{"s1", "string2", "s3"},
-			less:     func(a, b string) (bool, error) { return len(a) < len(b), nil },
-			wantValue: "s1",
-			wantIndex: 0,
-			wantErr:              false,
+			name:                  "success case",
+			input:                 []string{"s1", "string2", "s3"},
+			less:                  func(a, b string) (bool, error) { return len(a) < len(b), nil },
+			wantValue:             "s1",
+			wantIndex:             0,
+			wantErr:               false,
 			expectedCallbackCount: 2,
 		},
 		{
 			name:  "error on first comparison",
 			input: []string{"s1", "string2", "s3"},
 			less: func(a, b string) (bool, error) {
-				return false, fmt.Errorf("comparison error")
+				return false, errors.New("comparison error")
 			},
-			wantValue:            "",
-			wantIndex:            -1,
-			wantErr:              true,
-			errMsg:               "comparison error",
+			wantValue:             "",
+			wantIndex:             -1,
+			wantErr:               true,
+			errMsg:                "comparison error",
 			expectedCallbackCount: 1,
 		},
 		{
@@ -498,23 +499,23 @@ func TestMinIndexByErr(t *testing.T) {
 			input: []string{"a", "bb", "ccc", "error", "e"},
 			less: func(a, b string) (bool, error) {
 				if a == "error" || b == "error" {
-					return false, fmt.Errorf("error value encountered")
+					return false, errors.New("error value encountered")
 				}
 				return len(a) < len(b), nil
 			},
-			wantValue:            "",
-			wantIndex:            -1,
-			wantErr:              true,
-			errMsg:               "error value encountered",
+			wantValue:             "",
+			wantIndex:             -1,
+			wantErr:               true,
+			errMsg:                "error value encountered",
 			expectedCallbackCount: 3,
 		},
 		{
-			name:     "single element",
-			input:    []string{"single"},
-			less:     func(a, b string) (bool, error) { return len(a) < len(b), nil },
-			wantValue: "single",
-			wantIndex: 0,
-			wantErr:              false,
+			name:                  "single element",
+			input:                 []string{"single"},
+			less:                  func(a, b string) (bool, error) { return len(a) < len(b), nil },
+			wantValue:             "single",
+			wantIndex:             0,
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 	}
@@ -627,7 +628,10 @@ func TestEarliestByErr(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			result, err := EarliestByErr(tt.input, func(i foo) (time.Time, error) {
 				return i.bar, nil
 			})
@@ -664,7 +668,10 @@ func TestEarliestByErr(t *testing.T) {
 	}
 
 	for _, tt := range errorTests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			callbackCount := 0
 			_, err := EarliestByErr(tt.input, func(i foo) (time.Time, error) {
 				callbackCount++
@@ -775,9 +782,12 @@ func TestMaxByErr(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
-			result, err := MaxByErr(tt.input, func(item, max string) (bool, error) {
-				return len(item) > len(max), nil
+			t.Parallel()
+
+			result, err := MaxByErr(tt.input, func(item, mAx string) (bool, error) {
+				return len(item) > len(mAx), nil
 			})
 			is.NoError(err)
 			is.Equal(tt.expected, result)
@@ -806,14 +816,17 @@ func TestMaxByErr(t *testing.T) {
 	}
 
 	for _, tt := range errorTests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			callbackCount := 0
-			result, err := MaxByErr(tt.input, func(item, max string) (bool, error) {
+			result, err := MaxByErr(tt.input, func(item, mAx string) (bool, error) {
 				callbackCount++
 				if item == tt.errorAt {
 					return false, testErr
 				}
-				return len(item) > len(max), nil
+				return len(item) > len(mAx), nil
 			})
 			is.ErrorIs(err, testErr)
 			is.Equal(tt.expectedCalls, callbackCount)
@@ -897,9 +910,12 @@ func TestMaxIndexByErr(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
-			result, index, err := MaxIndexByErr(tt.input, func(item, max string) (bool, error) {
-				return len(item) > len(max), nil
+			t.Parallel()
+
+			result, index, err := MaxIndexByErr(tt.input, func(item, mAx string) (bool, error) {
+				return len(item) > len(mAx), nil
 			})
 			is.NoError(err)
 			is.Equal(tt.expectedResult, result)
@@ -935,14 +951,17 @@ func TestMaxIndexByErr(t *testing.T) {
 	}
 
 	for _, tt := range errorTests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			callbackCount := 0
-			result, index, err := MaxIndexByErr(tt.input, func(item, max string) (bool, error) {
+			result, index, err := MaxIndexByErr(tt.input, func(item, mAx string) (bool, error) {
 				callbackCount++
 				if item == tt.errorAt {
 					return false, testErr
 				}
-				return len(item) > len(max), nil
+				return len(item) > len(mAx), nil
 			})
 			is.ErrorIs(err, testErr)
 			is.Equal(tt.expectedCalls, callbackCount)
@@ -1029,7 +1048,10 @@ func TestLatestByErr(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			result, err := LatestByErr(tt.input, func(i foo) (time.Time, error) {
 				return i.bar, nil
 			})
@@ -1066,7 +1088,10 @@ func TestLatestByErr(t *testing.T) {
 	}
 
 	for _, tt := range errorTests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			callbackCount := 0
 			_, err := LatestByErr(tt.input, func(i foo) (time.Time, error) {
 				callbackCount++

intersect_test.go

@@ -1,7 +1,7 @@
 package lo
 
 import (
-	"fmt"
+	"errors"
 	"strconv"
 	"testing"
 
@@ -400,7 +400,7 @@ func TestWithoutByErr(t *testing.T) {
 			input: []User{{Name: "nick"}, {Name: "peter"}, {Name: "lily"}},
 			iteratee: func(item User) (string, error) {
 				if item.Name == "peter" {
-					return "", fmt.Errorf("peter not allowed")
+					return "", errors.New("peter not allowed")
 				}
 				return item.Name, nil
 			},
@@ -413,7 +413,7 @@ func TestWithoutByErr(t *testing.T) {
 			name:  "error on first element",
 			input: []User{{Name: "nick"}, {Name: "peter"}},
 			iteratee: func(item User) (string, error) {
-				return "", fmt.Errorf("first element error")
+				return "", errors.New("first element error")
 			},
 			exclude:       []string{"nick"},
 			want:          nil,

map_test.go

@@ -1,6 +1,7 @@
 package lo
 
 import (
+	"errors"
 	"fmt"
 	"strconv"
 	"testing"
@@ -173,7 +174,7 @@ func TestPickByErr(t *testing.T) {
 			input: map[string]int{"foo": 1, "bar": 2, "baz": 3},
 			predicate: func(key string, value int) (bool, error) {
 				if key == "bar" {
-					return false, fmt.Errorf("bar not allowed")
+					return false, errors.New("bar not allowed")
 				}
 				return true, nil
 			},
@@ -317,7 +318,7 @@ func TestOmitByErr(t *testing.T) {
 			input: map[string]int{"foo": 1, "bar": 2, "baz": 3},
 			predicate: func(key string, value int) (bool, error) {
 				if key == "bar" {
-					return false, fmt.Errorf("bar not allowed")
+					return false, errors.New("bar not allowed")
 				}
 				return true, nil
 			},
@@ -664,7 +665,7 @@ func TestMapValuesErr(t *testing.T) {
 			input: map[int]int{1: 1, 2: 2},
 			iteratee: func(x, _ int) (string, error) {
 				if x == 1 {
-					return "", fmt.Errorf("cannot process 1")
+					return "", errors.New("cannot process 1")
 				}
 				return strconv.FormatInt(int64(x), 10), nil
 			},
@@ -849,7 +850,7 @@ func TestMapEntriesErr(t *testing.T) {
 				input: map[string]int{"foo": 1, "bar": 2, "baz": 3},
 				iteratee: func(k string, v int) (string, int, error) {
 					if k == "bar" {
-						return "", 0, fmt.Errorf("bar not allowed")
+						return "", 0, errors.New("bar not allowed")
 					}
 					return k, v, nil
 				},
@@ -983,7 +984,7 @@ func TestMapEntriesErr(t *testing.T) {
 				input: map[string]int{"a": 1, "b": 2},
 				iteratee: func(k string, v int) (int, string, error) {
 					if k == "b" {
-						return 0, "", fmt.Errorf("cannot invert b")
+						return 0, "", errors.New("cannot invert b")
 					}
 					return v, k, nil
 				},
@@ -1031,75 +1032,75 @@ func TestMapToSliceErr(t *testing.T) {
 	t.Parallel()
 
 	tests := []struct {
-	 name          string
-	 input         map[int]int64
-	 iteratee      func(int, int64) (string, error)
-	 want          []string
-	 wantErr       string
-	 wantCallCount int // 0 means don't check (maps have no order)
+		name          string
+		input         map[int]int64
+		iteratee      func(int, int64) (string, error)
+		want          []string
+		wantErr       string
+		wantCallCount int // 0 means don't check (maps have no order)
 	}{
-	 {
-	 name:  "successful transformation",
-	 input: map[int]int64{1: 5, 2: 6, 3: 7},
-	 iteratee: func(k int, v int64) (string, error) {
-	 return fmt.Sprintf("%d_%d", k, v), nil
-	 },
-	 want:          []string{"1_5", "2_6", "3_7"},
-	 wantErr:       "",
-	 wantCallCount: 0, // map iteration order is not deterministic
-	 },
-	 {
-	 name:  "empty map",
-	 input: map[int]int64{},
-	 iteratee: func(k int, v int64) (string, error) {
-	 return fmt.Sprintf("%d_%d", k, v), nil
-	 },
-	 want:          []string{},
-	 wantErr:       "",
-	 wantCallCount: 0,
-	 },
-	 {
-	 name:  "error on specific key",
-	 input: map[int]int64{1: 5, 2: 6, 3: 7},
-	 iteratee: func(k int, v int64) (string, error) {
-	 if k == 2 {
-		 return "", fmt.Errorf("key 2 not allowed")
-	 }
-	 return fmt.Sprintf("%d_%d", k, v), nil
-	 },
-	 want:          nil,
-	 wantErr:       "key 2 not allowed",
-	 wantCallCount: 0, // map iteration order is not deterministic
-	 },
-	 {
-	 name:  "constant value",
-	 input: map[int]int64{1: 5, 2: 6, 3: 7},
-	 iteratee: func(k int, v int64) (string, error) {
-	 return "constant", nil
-	 },
-	 want:          []string{"constant", "constant", "constant"},
-	 wantErr:       "",
-	 wantCallCount: 0,
-	 },
+		{
+			name:  "successful transformation",
+			input: map[int]int64{1: 5, 2: 6, 3: 7},
+			iteratee: func(k int, v int64) (string, error) {
+				return fmt.Sprintf("%d_%d", k, v), nil
+			},
+			want:          []string{"1_5", "2_6", "3_7"},
+			wantErr:       "",
+			wantCallCount: 0, // map iteration order is not deterministic
+		},
+		{
+			name:  "empty map",
+			input: map[int]int64{},
+			iteratee: func(k int, v int64) (string, error) {
+				return fmt.Sprintf("%d_%d", k, v), nil
+			},
+			want:          []string{},
+			wantErr:       "",
+			wantCallCount: 0,
+		},
+		{
+			name:  "error on specific key",
+			input: map[int]int64{1: 5, 2: 6, 3: 7},
+			iteratee: func(k int, v int64) (string, error) {
+				if k == 2 {
+					return "", errors.New("key 2 not allowed")
+				}
+				return fmt.Sprintf("%d_%d", k, v), nil
+			},
+			want:          nil,
+			wantErr:       "key 2 not allowed",
+			wantCallCount: 0, // map iteration order is not deterministic
+		},
+		{
+			name:  "constant value",
+			input: map[int]int64{1: 5, 2: 6, 3: 7},
+			iteratee: func(k int, v int64) (string, error) {
+				return "constant", nil
+			},
+			want:          []string{"constant", "constant", "constant"},
+			wantErr:       "",
+			wantCallCount: 0,
+		},
 	}
 
 	for _, tt := range tests {
-	 tt := tt // capture range variable
-	 t.Run(tt.name, func(t *testing.T) {
-	 t.Parallel()
-	 is := assert.New(t)
+		tt := tt // capture range variable
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			is := assert.New(t)
 
-	 got, err := MapToSliceErr(tt.input, tt.iteratee)
+			got, err := MapToSliceErr(tt.input, tt.iteratee)
 
-	 if tt.wantErr != "" {
-		 is.Error(err)
-		 is.Equal(tt.wantErr, err.Error())
-		 is.Nil(got)
-	 } else {
-		 is.NoError(err)
-		 is.ElementsMatch(tt.want, got)
-	 }
-	 })
+			if tt.wantErr != "" {
+				is.Error(err)
+				is.Equal(tt.wantErr, err.Error())
+				is.Nil(got)
+			} else {
+				is.NoError(err)
+				is.ElementsMatch(tt.want, got)
+			}
+		})
 	}
 }
 

math_test.go

@@ -231,6 +231,7 @@ func TestProductBy(t *testing.T) {
 	is.Equal(uint32(1), result8)
 }
 
+//nolint:errcheck,forcetypeassert
 func TestProductByErr(t *testing.T) {
 	t.Parallel()
 	is := assert.New(t)
@@ -286,7 +287,10 @@ func TestProductByErr(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			switch input := tt.input.(type) {
 			case []float32:
 				result, err := ProductByErr(input, func(n float32) (float32, error) { return n, nil })
@@ -340,7 +344,10 @@ func TestProductByErr(t *testing.T) {
 	}
 
 	for _, tt := range errorTests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			callbackCount := 0
 			result, err := ProductByErr(tt.input, func(n int32) (int32, error) {
 				callbackCount++
@@ -386,6 +393,7 @@ func TestMeanBy(t *testing.T) {
 	is.Equal(uint32(0), result4)
 }
 
+//nolint:errcheck,forcetypeassert
 func TestMeanByErr(t *testing.T) {
 	t.Parallel()
 	is := assert.New(t)
@@ -426,7 +434,10 @@ func TestMeanByErr(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			switch input := tt.input.(type) {
 			case []float32:
 				result, err := MeanByErr(input, func(n float32) (float32, error) { return n, nil })
@@ -472,7 +483,10 @@ func TestMeanByErr(t *testing.T) {
 	}
 
 	for _, tt := range errorTests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			callbackCount := 0
 			_, err := MeanByErr(tt.input, func(n int32) (int32, error) {
 				callbackCount++

slice_test.go

@@ -1,6 +1,7 @@
 package lo
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"sort"
@@ -53,74 +54,74 @@ func TestMapErr(t *testing.T) {
 	is := assert.New(t)
 
 	tests := []struct {
-		name               string
-		input              []int
-		transform          func(item int, index int) (string, error)
-		wantResult         []string
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int
+		transform             func(item, index int) (string, error)
+		wantResult            []string
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
 			name:  "successful transformation",
 			input: []int{1, 2, 3, 4},
-			transform: func(x int, _ int) (string, error) {
+			transform: func(x, _ int) (string, error) {
 				return strconv.Itoa(x), nil
 			},
-			wantResult: []string{"1", "2", "3", "4"},
-			wantErr: false,
+			wantResult:            []string{"1", "2", "3", "4"},
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 		{
 			name:  "error at third element stops iteration",
 			input: []int{1, 2, 3, 4},
-			transform: func(x int, _ int) (string, error) {
+			transform: func(x, _ int) (string, error) {
 				if x == 3 {
-					return "", fmt.Errorf("number 3 is not allowed")
+					return "", errors.New("number 3 is not allowed")
 				}
 				return strconv.Itoa(x), nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 3 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 3 is not allowed",
 			expectedCallbackCount: 3,
 		},
 		{
 			name:  "error at first element stops iteration immediately",
 			input: []int{1, 2, 3, 4},
-			transform: func(x int, _ int) (string, error) {
+			transform: func(x, _ int) (string, error) {
 				if x == 1 {
-					return "", fmt.Errorf("number 1 is not allowed")
+					return "", errors.New("number 1 is not allowed")
 				}
 				return strconv.Itoa(x), nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 1 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 1 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
 			name:  "error at last element",
 			input: []int{1, 2, 3, 4},
-			transform: func(x int, _ int) (string, error) {
+			transform: func(x, _ int) (string, error) {
 				if x == 4 {
-					return "", fmt.Errorf("number 4 is not allowed")
+					return "", errors.New("number 4 is not allowed")
 				}
 				return strconv.Itoa(x), nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 4 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 4 is not allowed",
 			expectedCallbackCount: 4,
 		},
 		{
 			name:  "empty input slice",
 			input: []int{},
-			transform: func(x int, _ int) (string, error) {
+			transform: func(x, _ int) (string, error) {
 				return strconv.Itoa(x), nil
 			},
-			wantResult: []string{},
-			wantErr: false,
+			wantResult:            []string{},
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 	}
@@ -132,7 +133,7 @@ func TestMapErr(t *testing.T) {
 
 			// Track callback count to test early return
 			callbackCount := 0
-			wrappedTransform := func(item int, index int) (string, error) {
+			wrappedTransform := func(item, index int) (string, error) {
 				callbackCount++
 				return tt.transform(item, index)
 			}
@@ -218,12 +219,12 @@ func TestFlatMapErr(t *testing.T) {
 	is := assert.New(t)
 
 	tests := []struct {
-		name               string
-		input              []int64
-		transform          func(item int64, index int) ([]string, error)
-		wantResult         []string
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int64
+		transform             func(item int64, index int) ([]string, error)
+		wantResult            []string
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
@@ -232,8 +233,8 @@ func TestFlatMapErr(t *testing.T) {
 			transform: func(x int64, _ int) ([]string, error) {
 				return []string{strconv.FormatInt(x, 10), strconv.FormatInt(x, 10)}, nil
 			},
-			wantResult: []string{"0", "0", "1", "1", "2", "2"},
-			wantErr: false,
+			wantResult:            []string{"0", "0", "1", "1", "2", "2"},
+			wantErr:               false,
 			expectedCallbackCount: 3,
 		},
 		{
@@ -241,13 +242,13 @@ func TestFlatMapErr(t *testing.T) {
 			input: []int64{0, 1, 2, 3},
 			transform: func(x int64, _ int) ([]string, error) {
 				if x == 1 {
-					return nil, fmt.Errorf("number 1 is not allowed")
+					return nil, errors.New("number 1 is not allowed")
 				}
 				return []string{strconv.FormatInt(x, 10)}, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 1 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 1 is not allowed",
 			expectedCallbackCount: 2,
 		},
 		{
@@ -255,13 +256,13 @@ func TestFlatMapErr(t *testing.T) {
 			input: []int64{0, 1, 2, 3},
 			transform: func(x int64, _ int) ([]string, error) {
 				if x == 0 {
-					return nil, fmt.Errorf("number 0 is not allowed")
+					return nil, errors.New("number 0 is not allowed")
 				}
 				return []string{strconv.FormatInt(x, 10)}, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 0 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 0 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
@@ -269,13 +270,13 @@ func TestFlatMapErr(t *testing.T) {
 			input: []int64{0, 1, 2},
 			transform: func(x int64, _ int) ([]string, error) {
 				if x == 2 {
-					return nil, fmt.Errorf("number 2 is not allowed")
+					return nil, errors.New("number 2 is not allowed")
 				}
 				return []string{strconv.FormatInt(x, 10)}, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 2 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 2 is not allowed",
 			expectedCallbackCount: 3,
 		},
 		{
@@ -284,8 +285,8 @@ func TestFlatMapErr(t *testing.T) {
 			transform: func(x int64, _ int) ([]string, error) {
 				return []string{strconv.FormatInt(x, 10)}, nil
 			},
-			wantResult: []string{},
-			wantErr: false,
+			wantResult:            []string{},
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
@@ -294,8 +295,8 @@ func TestFlatMapErr(t *testing.T) {
 			transform: func(x int64, _ int) ([]string, error) {
 				return []string{}, nil
 			},
-			wantResult: []string{},
-			wantErr: false,
+			wantResult:            []string{},
+			wantErr:               false,
 			expectedCallbackCount: 3,
 		},
 		{
@@ -307,8 +308,8 @@ func TestFlatMapErr(t *testing.T) {
 				}
 				return []string{strconv.FormatInt(x, 10)}, nil
 			},
-			wantResult: []string{"1", "3"},
-			wantErr: false,
+			wantResult:            []string{"1", "3"},
+			wantErr:               false,
 			expectedCallbackCount: 3,
 		},
 	}
@@ -372,13 +373,13 @@ func TestReduceErr(t *testing.T) {
 	is := assert.New(t)
 
 	tests := []struct {
-		name               string
-		input              []int
-		accumulator        func(agg int, item int, index int) (int, error)
-		initial            int
-		wantResult         int
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int
+		accumulator           func(agg, item, index int) (int, error)
+		initial               int
+		wantResult            int
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
@@ -387,9 +388,9 @@ func TestReduceErr(t *testing.T) {
 			accumulator: func(agg, item, _ int) (int, error) {
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 10,
-			wantErr: false,
+			initial:               0,
+			wantResult:            10,
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 		{
@@ -397,14 +398,14 @@ func TestReduceErr(t *testing.T) {
 			input: []int{1, 2, 3, 4},
 			accumulator: func(agg, item, _ int) (int, error) {
 				if item == 3 {
-					return 0, fmt.Errorf("number 3 is not allowed")
+					return 0, errors.New("number 3 is not allowed")
 				}
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 0,
-			wantErr: true,
-			errMsg: "number 3 is not allowed",
+			initial:               0,
+			wantResult:            0,
+			wantErr:               true,
+			errMsg:                "number 3 is not allowed",
 			expectedCallbackCount: 3,
 		},
 		{
@@ -412,14 +413,14 @@ func TestReduceErr(t *testing.T) {
 			input: []int{1, 2, 3, 4},
 			accumulator: func(agg, item, _ int) (int, error) {
 				if item == 1 {
-					return 0, fmt.Errorf("number 1 is not allowed")
+					return 0, errors.New("number 1 is not allowed")
 				}
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 0,
-			wantErr: true,
-			errMsg: "number 1 is not allowed",
+			initial:               0,
+			wantResult:            0,
+			wantErr:               true,
+			errMsg:                "number 1 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
@@ -427,14 +428,14 @@ func TestReduceErr(t *testing.T) {
 			input: []int{1, 2, 3, 4},
 			accumulator: func(agg, item, _ int) (int, error) {
 				if item == 4 {
-					return 0, fmt.Errorf("number 4 is not allowed")
+					return 0, errors.New("number 4 is not allowed")
 				}
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 0,
-			wantErr: true,
-			errMsg: "number 4 is not allowed",
+			initial:               0,
+			wantResult:            0,
+			wantErr:               true,
+			errMsg:                "number 4 is not allowed",
 			expectedCallbackCount: 4,
 		},
 		{
@@ -443,9 +444,9 @@ func TestReduceErr(t *testing.T) {
 			accumulator: func(agg, item, _ int) (int, error) {
 				return agg + item, nil
 			},
-			initial: 10,
-			wantResult: 10,
-			wantErr: false,
+			initial:               10,
+			wantResult:            10,
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
@@ -454,9 +455,9 @@ func TestReduceErr(t *testing.T) {
 			accumulator: func(agg, item, _ int) (int, error) {
 				return agg + item, nil
 			},
-			initial: 10,
-			wantResult: 20,
-			wantErr: false,
+			initial:               10,
+			wantResult:            20,
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 	}
@@ -468,7 +469,7 @@ func TestReduceErr(t *testing.T) {
 
 			// Track callback count to test early return
 			callbackCount := 0
-			wrappedAccumulator := func(agg int, item int, index int) (int, error) {
+			wrappedAccumulator := func(agg, item, index int) (int, error) {
 				callbackCount++
 				return tt.accumulator(agg, item, index)
 			}
@@ -511,13 +512,13 @@ func TestReduceRightErr(t *testing.T) {
 	is := assert.New(t)
 
 	tests := []struct {
-		name               string
-		input              []int
-		accumulator        func(agg int, item int, index int) (int, error)
-		initial            int
-		wantResult         int
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int
+		accumulator           func(agg, item, index int) (int, error)
+		initial               int
+		wantResult            int
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
@@ -526,9 +527,9 @@ func TestReduceRightErr(t *testing.T) {
 			accumulator: func(agg, item, _ int) (int, error) {
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 10,
-			wantErr: false,
+			initial:               0,
+			wantResult:            10,
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 		{
@@ -536,14 +537,14 @@ func TestReduceRightErr(t *testing.T) {
 			input: []int{1, 2, 3, 4},
 			accumulator: func(agg, item, _ int) (int, error) {
 				if item == 3 {
-					return 0, fmt.Errorf("number 3 is not allowed")
+					return 0, errors.New("number 3 is not allowed")
 				}
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 0,
-			wantErr: true,
-			errMsg: "number 3 is not allowed",
+			initial:               0,
+			wantResult:            0,
+			wantErr:               true,
+			errMsg:                "number 3 is not allowed",
 			expectedCallbackCount: 2,
 		},
 		{
@@ -551,14 +552,14 @@ func TestReduceRightErr(t *testing.T) {
 			input: []int{1, 2, 3, 4},
 			accumulator: func(agg, item, _ int) (int, error) {
 				if item == 4 {
-					return 0, fmt.Errorf("number 4 is not allowed")
+					return 0, errors.New("number 4 is not allowed")
 				}
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 0,
-			wantErr: true,
-			errMsg: "number 4 is not allowed",
+			initial:               0,
+			wantResult:            0,
+			wantErr:               true,
+			errMsg:                "number 4 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
@@ -566,14 +567,14 @@ func TestReduceRightErr(t *testing.T) {
 			input: []int{1, 2, 3, 4},
 			accumulator: func(agg, item, _ int) (int, error) {
 				if item == 1 {
-					return 0, fmt.Errorf("number 1 is not allowed")
+					return 0, errors.New("number 1 is not allowed")
 				}
 				return agg + item, nil
 			},
-			initial: 0,
-			wantResult: 0,
-			wantErr: true,
-			errMsg: "number 1 is not allowed",
+			initial:               0,
+			wantResult:            0,
+			wantErr:               true,
+			errMsg:                "number 1 is not allowed",
 			expectedCallbackCount: 4,
 		},
 		{
@@ -582,9 +583,9 @@ func TestReduceRightErr(t *testing.T) {
 			accumulator: func(agg, item, _ int) (int, error) {
 				return agg + item, nil
 			},
-			initial: 10,
-			wantResult: 10,
-			wantErr: false,
+			initial:               10,
+			wantResult:            10,
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
@@ -593,9 +594,9 @@ func TestReduceRightErr(t *testing.T) {
 			accumulator: func(agg, item, _ int) (int, error) {
 				return agg + item, nil
 			},
-			initial: 10,
-			wantResult: 20,
-			wantErr: false,
+			initial:               10,
+			wantResult:            20,
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 	}
@@ -607,7 +608,7 @@ func TestReduceRightErr(t *testing.T) {
 
 			// Track callback count to test early return
 			callbackCount := 0
-			wrappedAccumulator := func(agg int, item int, index int) (int, error) {
+			wrappedAccumulator := func(agg, item, index int) (int, error) {
 				callbackCount++
 				return tt.accumulator(agg, item, index)
 			}
@@ -705,12 +706,12 @@ func TestUniqByErr(t *testing.T) {
 	is := assert.New(t)
 
 	tests := []struct {
-		name               string
-		input              []int
-		iteratee           func(item int) (int, error)
-		wantResult         []int
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int
+		iteratee              func(item int) (int, error)
+		wantResult            []int
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
@@ -719,8 +720,8 @@ func TestUniqByErr(t *testing.T) {
 			iteratee: func(i int) (int, error) {
 				return i % 3, nil
 			},
-			wantResult: []int{0, 1, 2},
-			wantErr: false,
+			wantResult:            []int{0, 1, 2},
+			wantErr:               false,
 			expectedCallbackCount: 6,
 		},
 		{
@@ -728,13 +729,13 @@ func TestUniqByErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			iteratee: func(i int) (int, error) {
 				if i == 3 {
-					return 0, fmt.Errorf("number 3 is not allowed")
+					return 0, errors.New("number 3 is not allowed")
 				}
 				return i % 3, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 3 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 3 is not allowed",
 			expectedCallbackCount: 4,
 		},
 		{
@@ -742,13 +743,13 @@ func TestUniqByErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			iteratee: func(i int) (int, error) {
 				if i == 0 {
-					return 0, fmt.Errorf("number 0 is not allowed")
+					return 0, errors.New("number 0 is not allowed")
 				}
 				return i % 3, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 0 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 0 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
@@ -756,13 +757,13 @@ func TestUniqByErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			iteratee: func(i int) (int, error) {
 				if i == 5 {
-					return 0, fmt.Errorf("number 5 is not allowed")
+					return 0, errors.New("number 5 is not allowed")
 				}
 				return i % 3, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 5 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 5 is not allowed",
 			expectedCallbackCount: 6,
 		},
 		{
@@ -771,8 +772,8 @@ func TestUniqByErr(t *testing.T) {
 			iteratee: func(i int) (int, error) {
 				return i % 3, nil
 			},
-			wantResult: []int{},
-			wantErr: false,
+			wantResult:            []int{},
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
@@ -781,8 +782,8 @@ func TestUniqByErr(t *testing.T) {
 			iteratee: func(i int) (int, error) {
 				return i % 3, nil
 			},
-			wantResult: []int{1},
-			wantErr: false,
+			wantResult:            []int{1},
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 		{
@@ -791,8 +792,8 @@ func TestUniqByErr(t *testing.T) {
 			iteratee: func(i int) (int, error) {
 				return i, nil
 			},
-			wantResult: []int{0, 1, 2, 3},
-			wantErr: false,
+			wantResult:            []int{0, 1, 2, 3},
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 	}
@@ -852,12 +853,12 @@ func TestGroupByErr(t *testing.T) {
 	is := assert.New(t)
 
 	tests := []struct {
-		name               string
-		input              []int
-		iteratee           func(item int) (int, error)
-		wantResult         map[int][]int
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int
+		iteratee              func(item int) (int, error)
+		wantResult            map[int][]int
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
@@ -871,7 +872,7 @@ func TestGroupByErr(t *testing.T) {
 				1: {1, 4},
 				2: {2, 5},
 			},
-			wantErr: false,
+			wantErr:               false,
 			expectedCallbackCount: 6,
 		},
 		{
@@ -879,13 +880,13 @@ func TestGroupByErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			iteratee: func(i int) (int, error) {
 				if i == 3 {
-					return 0, fmt.Errorf("number 3 is not allowed")
+					return 0, errors.New("number 3 is not allowed")
 				}
 				return i % 3, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 3 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 3 is not allowed",
 			expectedCallbackCount: 4,
 		},
 		{
@@ -893,13 +894,13 @@ func TestGroupByErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			iteratee: func(i int) (int, error) {
 				if i == 0 {
-					return 0, fmt.Errorf("number 0 is not allowed")
+					return 0, errors.New("number 0 is not allowed")
 				}
 				return i % 3, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 0 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 0 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
@@ -907,13 +908,13 @@ func TestGroupByErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			iteratee: func(i int) (int, error) {
 				if i == 5 {
-					return 0, fmt.Errorf("number 5 is not allowed")
+					return 0, errors.New("number 5 is not allowed")
 				}
 				return i % 3, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 5 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 5 is not allowed",
 			expectedCallbackCount: 6,
 		},
 		{
@@ -922,8 +923,8 @@ func TestGroupByErr(t *testing.T) {
 			iteratee: func(i int) (int, error) {
 				return i % 3, nil
 			},
-			wantResult: map[int][]int{},
-			wantErr: false,
+			wantResult:            map[int][]int{},
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
@@ -935,7 +936,7 @@ func TestGroupByErr(t *testing.T) {
 			wantResult: map[int][]int{
 				0: {3, 6, 9, 12},
 			},
-			wantErr: false,
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 	}
@@ -1019,12 +1020,12 @@ func TestGroupByMapErr(t *testing.T) {
 	is := assert.New(t)
 
 	tests := []struct {
-		name               string
-		input              []int
-		transform          func(item int) (int, int, error)
-		wantResult         map[int][]int
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int
+		transform             func(item int) (int, int, error)
+		wantResult            map[int][]int
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
@@ -1038,7 +1039,7 @@ func TestGroupByMapErr(t *testing.T) {
 				1: {2, 8},
 				2: {4, 10},
 			},
-			wantErr: false,
+			wantErr:               false,
 			expectedCallbackCount: 6,
 		},
 		{
@@ -1046,13 +1047,13 @@ func TestGroupByMapErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			transform: func(i int) (int, int, error) {
 				if i == 3 {
-					return 0, 0, fmt.Errorf("number 3 is not allowed")
+					return 0, 0, errors.New("number 3 is not allowed")
 				}
 				return i % 3, i * 2, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 3 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 3 is not allowed",
 			expectedCallbackCount: 4,
 		},
 		{
@@ -1060,13 +1061,13 @@ func TestGroupByMapErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			transform: func(i int) (int, int, error) {
 				if i == 0 {
-					return 0, 0, fmt.Errorf("number 0 is not allowed")
+					return 0, 0, errors.New("number 0 is not allowed")
 				}
 				return i % 3, i * 2, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 0 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 0 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
@@ -1074,13 +1075,13 @@ func TestGroupByMapErr(t *testing.T) {
 			input: []int{0, 1, 2, 3, 4, 5},
 			transform: func(i int) (int, int, error) {
 				if i == 5 {
-					return 0, 0, fmt.Errorf("number 5 is not allowed")
+					return 0, 0, errors.New("number 5 is not allowed")
 				}
 				return i % 3, i * 2, nil
 			},
-			wantResult: nil,
-			wantErr: true,
-			errMsg: "number 5 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 5 is not allowed",
 			expectedCallbackCount: 6,
 		},
 		{
@@ -1089,8 +1090,8 @@ func TestGroupByMapErr(t *testing.T) {
 			transform: func(i int) (int, int, error) {
 				return i % 3, i * 2, nil
 			},
-			wantResult: map[int][]int{},
-			wantErr: false,
+			wantResult:            map[int][]int{},
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
@@ -1102,7 +1103,7 @@ func TestGroupByMapErr(t *testing.T) {
 			wantResult: map[int][]int{
 				0: {3, 6, 9, 12},
 			},
-			wantErr: false,
+			wantErr:               false,
 			expectedCallbackCount: 4,
 		},
 	}
@@ -1296,80 +1297,80 @@ func TestPartitionByErr(t *testing.T) {
 	}
 
 	tests := []struct {
-		name               string
-		input              []int
-		iteratee           func(item int) (string, error)
-		wantResult         [][]int
-		wantErr            bool
-		errMsg             string
+		name                  string
+		input                 []int
+		iteratee              func(item int) (string, error)
+		wantResult            [][]int
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
-			name:       "successful partition",
-			input:      []int{-2, -1, 0, 1, 2, 3, 4, 5},
-			iteratee:   oddEven,
-			wantResult: [][]int{{-2, -1}, {0, 2, 4}, {1, 3, 5}},
-			wantErr:    false,
+			name:                  "successful partition",
+			input:                 []int{-2, -1, 0, 1, 2, 3, 4, 5},
+			iteratee:              oddEven,
+			wantResult:            [][]int{{-2, -1}, {0, 2, 4}, {1, 3, 5}},
+			wantErr:               false,
 			expectedCallbackCount: 8,
 		},
 		{
-			name: "error at fifth element stops iteration",
+			name:  "error at fifth element stops iteration",
 			input: []int{-2, -1, 0, 1, 2, 3},
 			iteratee: func(x int) (string, error) {
 				if x == 2 {
-					return "", fmt.Errorf("number 2 is not allowed")
+					return "", errors.New("number 2 is not allowed")
 				}
 				return oddEven(x)
 			},
-			wantResult: nil,
-			wantErr:    true,
-			errMsg:     "number 2 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 2 is not allowed",
 			expectedCallbackCount: 5,
 		},
 		{
-			name: "error at first element stops iteration immediately",
+			name:  "error at first element stops iteration immediately",
 			input: []int{-2, -1, 0, 1},
 			iteratee: func(x int) (string, error) {
 				if x == -2 {
-					return "", fmt.Errorf("number -2 is not allowed")
+					return "", errors.New("number -2 is not allowed")
 				}
 				return oddEven(x)
 			},
-			wantResult: nil,
-			wantErr:    true,
-			errMsg:     "number -2 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number -2 is not allowed",
 			expectedCallbackCount: 1,
 		},
 		{
-			name: "error at last element",
+			name:  "error at last element",
 			input: []int{-2, -1, 0, 1, 2},
 			iteratee: func(x int) (string, error) {
 				if x == 2 {
-					return "", fmt.Errorf("number 2 is not allowed")
+					return "", errors.New("number 2 is not allowed")
 				}
 				return oddEven(x)
 			},
-			wantResult: nil,
-			wantErr:    true,
-			errMsg:     "number 2 is not allowed",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "number 2 is not allowed",
 			expectedCallbackCount: 5,
 		},
 		{
-			name:       "empty input slice",
-			input:      []int{},
-			iteratee:   oddEven,
-			wantResult: [][]int{},
-			wantErr:    false,
+			name:                  "empty input slice",
+			input:                 []int{},
+			iteratee:              oddEven,
+			wantResult:            [][]int{},
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
-			name: "all elements in same partition",
+			name:  "all elements in same partition",
 			input: []int{1, 3, 5},
 			iteratee: func(x int) (string, error) {
 				return "odd", nil
 			},
-			wantResult: [][]int{{1, 3, 5}},
-			wantErr:    false,
+			wantResult:            [][]int{{1, 3, 5}},
+			wantErr:               false,
 			expectedCallbackCount: 3,
 		},
 	}
@@ -1574,75 +1575,75 @@ func TestKeyByErr(t *testing.T) {
 	t.Parallel()
 
 	tests := []struct {
-		name                 string
-		input                []string
-		iteratee             func(item string) (int, error)
-		wantResult           map[int]string
-		wantErr              bool
-		errMsg               string
+		name                  string
+		input                 []string
+		iteratee              func(item string) (int, error)
+		wantResult            map[int]string
+		wantErr               bool
+		errMsg                string
 		expectedCallbackCount int
 	}{
 		{
-			name:     "empty slice",
-			input:    []string{},
-			iteratee: func(s string) (int, error) { return len(s), nil },
-			wantResult: map[int]string{},
-			wantErr:              false,
+			name:                  "empty slice",
+			input:                 []string{},
+			iteratee:              func(s string) (int, error) { return len(s), nil },
+			wantResult:            map[int]string{},
+			wantErr:               false,
 			expectedCallbackCount: 0,
 		},
 		{
-			name:     "success case",
-			input:    []string{"a", "aa", "aaa"},
-			iteratee: func(s string) (int, error) { return len(s), nil },
-			wantResult: map[int]string{1: "a", 2: "aa", 3: "aaa"},
-			wantErr:              false,
+			name:                  "success case",
+			input:                 []string{"a", "aa", "aaa"},
+			iteratee:              func(s string) (int, error) { return len(s), nil },
+			wantResult:            map[int]string{1: "a", 2: "aa", 3: "aaa"},
+			wantErr:               false,
 			expectedCallbackCount: 3,
 		},
 		{
-			name: "error stops iteration - first item",
+			name:  "error stops iteration - first item",
 			input: []string{"a", "aa", "aaa"},
 			iteratee: func(s string) (int, error) {
 				return 0, fmt.Errorf("error on %s", s)
 			},
-			wantResult:           nil,
-			wantErr:              true,
-			errMsg:               "error on a",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "error on a",
 			expectedCallbackCount: 1,
 		},
 		{
-			name: "error stops iteration - middle item",
+			name:  "error stops iteration - middle item",
 			input: []string{"a", "aa", "aaa"},
 			iteratee: func(s string) (int, error) {
 				if s == "aa" {
-					return 0, fmt.Errorf("middle error")
+					return 0, errors.New("middle error")
 				}
 				return len(s), nil
 			},
-			wantResult:           nil,
-			wantErr:              true,
-			errMsg:               "middle error",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "middle error",
 			expectedCallbackCount: 2,
 		},
 		{
-			name: "error stops iteration - last item",
+			name:  "error stops iteration - last item",
 			input: []string{"a", "aa", "aaa"},
 			iteratee: func(s string) (int, error) {
 				if s == "aaa" {
-					return 0, fmt.Errorf("last error")
+					return 0, errors.New("last error")
 				}
 				return len(s), nil
 			},
-			wantResult:           nil,
-			wantErr:              true,
-			errMsg:               "last error",
+			wantResult:            nil,
+			wantErr:               true,
+			errMsg:                "last error",
 			expectedCallbackCount: 3,
 		},
 		{
-			name:     "duplicate keys",
-			input:    []string{"a", "b", "c"},
-			iteratee: func(s string) (int, error) { return 1, nil },
-			wantResult: map[int]string{1: "c"},
-			wantErr:              false,
+			name:                  "duplicate keys",
+			input:                 []string{"a", "b", "c"},
+			iteratee:              func(s string) (int, error) { return 1, nil },
+			wantResult:            map[int]string{1: "c"},
+			wantErr:               false,
 			expectedCallbackCount: 3,
 		},
 	}
@@ -2272,7 +2273,7 @@ func TestCountByErr(t *testing.T) {
 			name:  "error on first element",
 			input: []int{1, 2, 3},
 			predicate: func(i int) (bool, error) {
-				return false, fmt.Errorf("first element error")
+				return false, errors.New("first element error")
 			},
 			want:          0,
 			wantErr:       "first element error",