add NoError assertion

assert/Asserter.go

@@ -723,3 +723,16 @@ func (a Asserter) ErrorIs(expected, actual error, msg ...any) {
 		UserMessage: msg,
 	})
 }
+
+func (a Asserter) NoError(err error, msg ...any) {
+	a.TB.Helper()
+	if err == nil {
+		return
+	}
+	a.Fn(fmterror.Message{
+		Method:      "NoError",
+		Cause:       "Non-nil error value is received.",
+		Values:      []fmterror.Value{{Label: "error", Value: err}},
+		UserMessage: msg,
+	})
+}

assert/Asserter_test.go

@@ -1347,3 +1347,24 @@ func TestAsserter_ErrorIs(t *testing.T) {
 		})
 	}
 }
+
+func TestAsserter_NoError(t *testing.T) {
+	t.Run(`when nil passed, then it is accepted`, func(t *testing.T) {
+		var failed bool
+		subject := asserter(func(args ...interface{}) { failed = true })
+		subject.NoError(nil)
+		Equal(t, failed, false)
+	})
+	t.Run(`when non-nil error value is passed`, func(t *testing.T) {
+		var failed bool
+		var actualMsg []interface{}
+		subject := asserter(func(args ...interface{}) {
+			failed = true
+			actualMsg = args
+		})
+		expectedMsg := []interface{}{"foo", "bar", "baz"}
+		subject.NoError(errors.New("boom"), expectedMsg...)
+		Equal(t, failed, true)
+		AssertFailFnArgs(t, expectedMsg, actualMsg)
+	})
+}

assert/example_test.go

@@ -500,3 +500,16 @@ func ExampleEventually_byCustomRetryStrategy() {
 		}
 	})
 }
+
+func ExampleAsserter_NoError() {
+	var tb testing.TB
+	asserter := assert.Should(tb)
+	asserter.NoError(nil)                // passes
+	asserter.NoError(errors.New("boom")) // fails
+}
+
+func ExampleNoError() {
+	var tb testing.TB
+	assert.NoError(tb, nil)                // passes
+	assert.NoError(tb, errors.New("boom")) // fails
+}

assert/pkgfunc.go

@@ -73,3 +73,8 @@ func ErrorIs(tb testing.TB, expected, actual error, msg ...any) {
 	tb.Helper()
 	Must(tb).ErrorIs(expected, actual, msg...)
 }
+
+func NoError(tb testing.TB, err error, msg ...any) {
+	tb.Helper()
+	Must(tb).NoError(err, msg...)
+}

assert/pkgfunc_test.go

@@ -245,6 +245,21 @@ func TestPublicFunctions(t *testing.T) {
 				assert.ErrorIs(tb, expected, actual)
 			},
 		},
+		// .ErrorIs
+		{
+			Desc:   ".NoError - happy",
+			Failed: false,
+			Assert: func(tb testing.TB) {
+				assert.NoError(tb, nil)
+			},
+		},
+		{
+			Desc:   ".NoError - rainy",
+			Failed: true,
+			Assert: func(tb testing.TB) {
+				assert.NoError(tb, errors.New("boom"))
+			},
+		},
 	} {
 		t.Run(tc.Desc, func(t *testing.T) {
 			stub := &testcase.StubTB{}