1 files changed, 80 insertions, 0 deletions
diff --git a/src/testing/helperfuncs_test.go b/src/testing/helperfuncs_test.go
new file mode 100644
index 0000000..df0476e
--- /dev/null
+++ b/src/testing/helperfuncs_test.go
@@ -0,0 +1,80 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testing
+
+import "sync"
+
+// The line numbering of this file is important for TestTBHelper.
+
+func notHelper(t *T, msg string) {
+	t.Error(msg)
+}
+
+func helper(t *T, msg string) {
+	t.Helper()
+	t.Error(msg)
+}
+
+func notHelperCallingHelper(t *T, msg string) {
+	helper(t, msg)
+}
+
+func helperCallingHelper(t *T, msg string) {
+	t.Helper()
+	helper(t, msg)
+}
+
+func testHelper(t *T) {
+	// Check combinations of directly and indirectly
+	// calling helper functions.
+	notHelper(t, "0")
+	helper(t, "1")
+	notHelperCallingHelper(t, "2")
+	helperCallingHelper(t, "3")
+
+	// Check a function literal closing over t that uses Helper.
+	fn := func(msg string) {
+		t.Helper()
+		t.Error(msg)
+	}
+	fn("4")
+
+	t.Run("sub", func(t *T) {
+		helper(t, "5")
+		notHelperCallingHelper(t, "6")
+		// Check that calling Helper from inside a subtest entry function
+		// works as if it were in an ordinary function call.
+		t.Helper()
+		t.Error("7")
+	})
+
+	// Check that calling Helper from inside a top-level test function
+	// has no effect.
+	t.Helper()
+	t.Error("8")
+
+	// Check that right caller is reported for func passed to Cleanup when
+	// multiple cleanup functions have been registered.
+	t.Cleanup(func() {
+		t.Helper()
+		t.Error("10")
+	})
+	t.Cleanup(func() {
+		t.Helper()
+		t.Error("9")
+	})
+}
+
+func parallelTestHelper(t *T) {
+	var wg sync.WaitGroup
+	for i := 0; i < 5; i++ {
+		wg.Add(1)
+		go func() {
+			notHelperCallingHelper(t, "parallel")
+			wg.Done()
+		}()
+	}
+	wg.Wait()
+}