efficientgo · bwplotka · Dec 1, 2022 · Dec 1, 2022 · Dec 1, 2022
diff --git a/merrors/doc.go b/merrors/doc.go
@@ -19,12 +19,11 @@
 //
 // Example 3:
 //
-//	func CloseAll(closers []io.Closer) error {
-//		errs := merrors.New()
-//		for _ , c := range closers {
-//			errs.Add(c.Close())
-//    	}
-//		return errs.Err()
-//	}
-//
+//		func CloseAll(closers []io.Closer) error {
+//			errs := merrors.New()
+//			for _ , c := range closers {
+//				errs.Add(c.Close())
+//	   	}
+//			return errs.Err()
+//		}
 package merrors
diff --git a/testutil/testutil.go b/testutil/testutil.go
@@ -92,6 +92,52 @@ func FaultOrPanicToErr(f func()) (err error) {
 	return err
 }
 
+// ContainsStringSlice fails the test if needle is not contained within haystack, if haystack or needle is
+// an empty slice, or if needle is longer than haystack.
+func ContainsStringSlice(tb testing.TB, haystack, needle []string) {
+	_, file, line, _ := runtime.Caller(1)
+
+	if !contains(haystack, needle) {
+		tb.Fatalf(sprintfWithLimit("\033[31m%s:%d: %#v does not contain %#v\033[39m\n\n", filepath.Base(file), line, haystack, needle))
+	}
+}
+
+func contains(haystack, needle []string) bool {
+	if len(haystack) == 0 || len(needle) == 0 {
+		return false
+	}
+
+	if len(haystack) < len(needle) {
+		return false
+	}
+
+	for i := 0; i < len(haystack); i++ {
+		outer := i
+
+		for j := 0; j < len(needle); j++ {
+			// End of the haystack but not the end of the needle, end
+			if outer == len(haystack) {
+				return false
+			}
+
+			// No match, try the next index of the haystack
+			if haystack[outer] != needle[j] {
+				break
+			}
+
+			// End of the needle and it still matches, end
+			if j == len(needle)-1 {
+				return true
+			}
+
+			// This element matches between the two slices, try the next one
+			outer++
+		}
+	}
+
+	return false
+}
+
 func sprintfWithLimit(act string, v ...interface{}) string {
 	s := fmt.Sprintf(act, v...)
 	if len(s) > 10000 {

diff --git a/testutil/testutil_test.go b/testutil/testutil_test.go
@@ -0,0 +1,70 @@
+// Copyright (c) The EfficientGo Authors.
+// Licensed under the Apache License 2.0.
+
+package testutil
+
+import "testing"
+
+func TestContains(t *testing.T) {
+	tests := map[string]struct {
+		haystack    []string
+		needle      []string
+		shouldMatch bool
+	}{
+		"empty haystack": {
+			haystack:    []string{},
+			needle:      []string{"key1"},
+			shouldMatch: false,
+		},
+
+		"empty needle": {
+			haystack:    []string{"key1", "key2", "key3"},
+			needle:      []string{},
+			shouldMatch: false,
+		},
+
+		"single value needle": {
+			haystack:    []string{"key1", "key2", "key3"},
+			needle:      []string{"key1"},
+			shouldMatch: true,
+		},
+
+		"multiple value needle": {
+			haystack:    []string{"key1", "key2", "key3"},
+			needle:      []string{"key1", "key2"},
+			shouldMatch: true,
+		},
+
+		"same size needle as haystack": {
+			haystack:    []string{"key1", "key2", "key3"},
+			needle:      []string{"key1", "key2", "key3"},
+			shouldMatch: true,
+		},
+
+		"larger needle than haystack": {
+			haystack:    []string{"key1", "key2", "key3"},
+			needle:      []string{"key1", "key2", "key3", "key4"},
+			shouldMatch: false,
+		},
+
+		"needle not contained": {
+			haystack:    []string{"key1", "key2", "key3"},
+			needle:      []string{"key4"},
+			shouldMatch: false,
+		},
+
+		"haystack ends before needle": {
+			haystack:    []string{"key1", "key2", "key3"},
+			needle:      []string{"key3", "key4"},
+			shouldMatch: false,
+		},
+	}
+
+	for testName, testData := range tests {
+		t.Run(testName, func(t *testing.T) {
+			if testData.shouldMatch != contains(testData.haystack, testData.needle) {
+				t.Fatalf("unexpected result testing contains() with %#v", testData)
+			}
+		})
+	}
+}