1 files changed, 83 insertions, 0 deletions
diff --git a/src/testing/testing_test.go b/src/testing/testing_test.go
index 0f096980ca..55a4df4739 100644
--- a/src/testing/testing_test.go
+++ b/src/testing/testing_test.go
@@ -109,3 +109,86 @@ func testTempDir(t *testing.T) {
 		t.Errorf("unexpected %d files in TempDir: %v", len(files), files)
 	}
 }
+
+func TestSetenv(t *testing.T) {
+	tests := []struct {
+		name               string
+		key                string
+		initialValueExists bool
+		initialValue       string
+		newValue           string
+	}{
+		{
+			name:               "initial value exists",
+			key:                "GO_TEST_KEY_1",
+			initialValueExists: true,
+			initialValue:       "111",
+			newValue:           "222",
+		},
+		{
+			name:               "initial value exists but empty",
+			key:                "GO_TEST_KEY_2",
+			initialValueExists: true,
+			initialValue:       "",
+			newValue:           "222",
+		},
+		{
+			name:               "initial value is not exists",
+			key:                "GO_TEST_KEY_3",
+			initialValueExists: false,
+			initialValue:       "",
+			newValue:           "222",
+		},
+	}
+
+	for _, test := range tests {
+		if test.initialValueExists {
+			if err := os.Setenv(test.key, test.initialValue); err != nil {
+				t.Fatalf("unable to set env: got %v", err)
+			}
+		} else {
+			os.Unsetenv(test.key)
+		}
+
+		t.Run(test.name, func(t *testing.T) {
+			t.Setenv(test.key, test.newValue)
+			if os.Getenv(test.key) != test.newValue {
+				t.Fatalf("unexpected value after t.Setenv: got %s, want %s", os.Getenv(test.key), test.newValue)
+			}
+		})
+
+		got, exists := os.LookupEnv(test.key)
+		if got != test.initialValue {
+			t.Fatalf("unexpected value after t.Setenv cleanup: got %s, want %s", got, test.initialValue)
+		}
+		if exists != test.initialValueExists {
+			t.Fatalf("unexpected value after t.Setenv cleanup: got %t, want %t", exists, test.initialValueExists)
+		}
+	}
+}
+
+func TestSetenvWithParallelAfterSetenv(t *testing.T) {
+	defer func() {
+		want := "testing: t.Parallel called after t.Setenv; cannot set environment variables in parallel tests"
+		if got := recover(); got != want {
+			t.Fatalf("expected panic; got %#v want %q", got, want)
+		}
+	}()
+
+	t.Setenv("GO_TEST_KEY_1", "value")
+
+	t.Parallel()
+}
+
+func TestSetenvWithParallelBeforeSetenv(t *testing.T) {
+	defer func() {
+		want := "testing: t.Setenv called after t.Parallel; cannot set environment variables in parallel tests"
+		if got := recover(); got != want {
+			t.Fatalf("expected panic; got %#v want %q", got, want)
+		}
+	}()
+
+	t.Parallel()
+
+	t.Setenv("GO_TEST_KEY_1", "value")
+}