Merge pull request #10 from JosiahWitt/add-is-nil

Add IsNil() chained function

ensurepkg/chain.go

@@ -39,22 +39,23 @@ func (c Chain) IsFalse() {
 	}
 }
 
+// IsNil ensures the actual value is nil or a nil pointer.
+func (c Chain) IsNil() {
+	c.t.Helper()
+
+	if !isNil(c.actual) {
+		c.t.Errorf("Got %+v, expected nil", c.actual)
+	}
+}
+
 // Equals ensures the actual value equals the expected value.
 // Equals uses deep.Equal to print easy to read diffs.
 func (c Chain) Equals(expected interface{}) {
 	c.t.Helper()
 
 	// If we expect nil, return early if actual is nil or if it is a nil pointer
-	if expected == nil {
-		if c.actual == nil {
-			return
-		}
-
-		actualReflection := reflect.ValueOf(c.actual)
-		isActualNilPointer := actualReflection.Kind() == reflect.Ptr && actualReflection.IsNil()
-		if isActualNilPointer {
-			return
-		}
+	if expected == nil && isNil(c.actual) {
+		return
 	}
 
 	deep.CompareUnexportedFields = true
@@ -89,7 +90,7 @@ func (c Chain) IsError(expected error) {
 	if !errors.Is(actual, expected) {
 		actualOutput := buildActualErrorOutput(actual)
 		expectedOutput := buildExpectedErrorOutput(expected)
-		c.t.Errorf("\nGot:      %s\nExpected: %s", actualOutput, expectedOutput)
+		c.t.Errorf("\nActual error is not the expected error:\n\tActual:   %s\n\tExpected: %s", actualOutput, expectedOutput)
 	}
 }
 
@@ -127,3 +128,13 @@ func buildExpectedErrorOutput(expected error) string {
 		expectedErk.Params(),
 	)
 }
+
+func isNil(value interface{}) bool {
+	if value == nil {
+		return true
+	}
+
+	reflection := reflect.ValueOf(value)
+	isNilPointer := reflection.Kind() == reflect.Ptr && reflection.IsNil()
+	return isNilPointer
+}

ensurepkg/chain_test.go

@@ -83,6 +83,41 @@ func TestChainIsFalse(t *testing.T) {
 	})
 }
 
+func TestChainIsNil(t *testing.T) {
+	t.Run("when nil", func(t *testing.T) {
+		ctrl := gomock.NewController(t)
+		mockT := mock_ensurepkg.NewMockT(ctrl)
+		mockT.EXPECT().Helper()
+
+		ensure := ensure.New(mockT)
+		ensure(nil).IsNil()
+	})
+
+	t.Run("when nil pointer", func(t *testing.T) {
+		ctrl := gomock.NewController(t)
+		mockT := mock_ensurepkg.NewMockT(ctrl)
+		mockT.EXPECT().Helper()
+
+		var nilPtr *string
+
+		ensure := ensure.New(mockT)
+		ensure(nilPtr).IsNil()
+	})
+
+	t.Run("when not nil", func(t *testing.T) {
+		ctrl := gomock.NewController(t)
+		mockT := mock_ensurepkg.NewMockT(ctrl)
+
+		const val = "not nil"
+		mockT.EXPECT().Errorf("Got %+v, expected nil", val).After(
+			mockT.EXPECT().Helper(),
+		)
+
+		ensure := ensure.New(mockT)
+		ensure(val).IsNil()
+	})
+}
+
 func TestChainEquals(t *testing.T) {
 	const errorMessageFormat = "\n%s\n\nActual:   %+v\nExpected: %+v"
 
@@ -275,7 +310,7 @@ func TestChainEquals(t *testing.T) {
 }
 
 func TestChainIsError(t *testing.T) {
-	const errorFormat = "\nGot:      %s\nExpected: %s"
+	const errorFormat = "\nActual error is not the expected error:\n\tActual:   %s\n\tExpected: %s"
 
 	t.Run("when equal error by reference", func(t *testing.T) {
 		ctrl := gomock.NewController(t)
@@ -474,7 +509,7 @@ func TestChainIsNotError(t *testing.T) {
 		mockT := mock_ensurepkg.NewMockT(ctrl)
 
 		err := errors.New("my error")
-		mockT.EXPECT().Errorf("\nGot:      %s\nExpected: %s", err.Error(), "<nil>").After(
+		mockT.EXPECT().Errorf("\nActual error is not the expected error:\n\tActual:   %s\n\tExpected: %s", err.Error(), "<nil>").After(
 			mockT.EXPECT().Helper().Times(2),
 		)