Add NotImplements and variants

assert/assertion_format.go

@@ -616,6 +616,16 @@ func NotErrorIsf(t TestingT, err error, target error, msg string, args ...interf
 	return NotErrorIs(t, err, target, append([]interface{}{msg}, args...)...)
 }
 
+// NotImplementsf asserts that an object does not implement the specified interface.
+//
+//	assert.NotImplementsf(t, (*MyInterface)(nil), new(MyObject), "error message %s", "formatted")
+func NotImplementsf(t TestingT, interfaceObject interface{}, object interface{}, msg string, args ...interface{}) bool {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+	return NotImplements(t, interfaceObject, object, append([]interface{}{msg}, args...)...)
+}
+
 // NotNilf asserts that the specified object is not nil.
 //
 //	assert.NotNilf(t, err, "error message %s", "formatted")

assert/assertion_forward.go

@@ -1221,6 +1221,26 @@ func (a *Assertions) NotErrorIsf(err error, target error, msg string, args ...in
 	return NotErrorIsf(a.t, err, target, msg, args...)
 }
 
+// NotImplements asserts that an object does not implement the specified interface.
+//
+//	a.NotImplements((*MyInterface)(nil), new(MyObject))
+func (a *Assertions) NotImplements(interfaceObject interface{}, object interface{}, msgAndArgs ...interface{}) bool {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	return NotImplements(a.t, interfaceObject, object, msgAndArgs...)
+}
+
+// NotImplementsf asserts that an object does not implement the specified interface.
+//
+//	a.NotImplementsf((*MyInterface)(nil), new(MyObject), "error message %s", "formatted")
+func (a *Assertions) NotImplementsf(interfaceObject interface{}, object interface{}, msg string, args ...interface{}) bool {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	return NotImplementsf(a.t, interfaceObject, object, msg, args...)
+}
+
 // NotNil asserts that the specified object is not nil.
 //
 //	a.NotNil(err)

assert/assertions.go

@@ -382,6 +382,25 @@ func Implements(t TestingT, interfaceObject interface{}, object interface{}, msg
 	return true
 }
 
+// NotImplements asserts that an object does not implement the specified interface.
+//
+//	assert.NotImplements(t, (*MyInterface)(nil), new(MyObject))
+func NotImplements(t TestingT, interfaceObject interface{}, object interface{}, msgAndArgs ...interface{}) bool {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+	interfaceType := reflect.TypeOf(interfaceObject).Elem()
+
+	if object == nil {
+		return Fail(t, fmt.Sprintf("Cannot check if nil does not implement %v", interfaceType), msgAndArgs...)
+	}
+	if reflect.TypeOf(object).Implements(interfaceType) {
+		return Fail(t, fmt.Sprintf("%T implements %v", object, interfaceType), msgAndArgs...)
+	}
+
+	return true
+}
+
 // IsType asserts that the specified objects are of the same type.
 func IsType(t TestingT, expectedType interface{}, object interface{}, msgAndArgs ...interface{}) bool {
 	if h, ok := t.(tHelper); ok {

assert/assertions_test.go

@@ -438,6 +438,22 @@ func TestImplements(t *testing.T) {
 
 }
 
+func TestNotImplements(t *testing.T) {
+
+	mockT := new(testing.T)
+
+	if !NotImplements(mockT, (*AssertionTesterInterface)(nil), new(AssertionTesterNonConformingObject)) {
+		t.Error("NotImplements method should return true: AssertionTesterNonConformingObject does not implement AssertionTesterInterface")
+	}
+	if NotImplements(mockT, (*AssertionTesterInterface)(nil), new(AssertionTesterConformingObject)) {
+		t.Error("NotImplements method should return false: AssertionTesterConformingObject implements AssertionTesterInterface")
+	}
+	if NotImplements(mockT, (*AssertionTesterInterface)(nil), nil) {
+		t.Error("NotImplements method should return false: nil can't be checked to be implementing AssertionTesterInterface or not")
+	}
+
+}
+
 func TestIsType(t *testing.T) {
 
 	mockT := new(testing.T)

require/require.go

@@ -1546,6 +1546,32 @@ func NotErrorIsf(t TestingT, err error, target error, msg string, args ...interf
 	t.FailNow()
 }
 
+// NotImplements asserts that an object does not implement the specified interface.
+//
+//	assert.NotImplements(t, (*MyInterface)(nil), new(MyObject))
+func NotImplements(t TestingT, interfaceObject interface{}, object interface{}, msgAndArgs ...interface{}) {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+	if assert.NotImplements(t, interfaceObject, object, msgAndArgs...) {
+		return
+	}
+	t.FailNow()
+}
+
+// NotImplementsf asserts that an object does not implement the specified interface.
+//
+//	assert.NotImplementsf(t, (*MyInterface)(nil), new(MyObject), "error message %s", "formatted")
+func NotImplementsf(t TestingT, interfaceObject interface{}, object interface{}, msg string, args ...interface{}) {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+	if assert.NotImplementsf(t, interfaceObject, object, msg, args...) {
+		return
+	}
+	t.FailNow()
+}
+
 // NotNil asserts that the specified object is not nil.
 //
 //	assert.NotNil(t, err)

require/require_forward.go

@@ -1222,6 +1222,26 @@ func (a *Assertions) NotErrorIsf(err error, target error, msg string, args ...in
 	NotErrorIsf(a.t, err, target, msg, args...)
 }
 
+// NotImplements asserts that an object does not implement the specified interface.
+//
+//	a.NotImplements((*MyInterface)(nil), new(MyObject))
+func (a *Assertions) NotImplements(interfaceObject interface{}, object interface{}, msgAndArgs ...interface{}) {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	NotImplements(a.t, interfaceObject, object, msgAndArgs...)
+}
+
+// NotImplementsf asserts that an object does not implement the specified interface.
+//
+//	a.NotImplementsf((*MyInterface)(nil), new(MyObject), "error message %s", "formatted")
+func (a *Assertions) NotImplementsf(interfaceObject interface{}, object interface{}, msg string, args ...interface{}) {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	NotImplementsf(a.t, interfaceObject, object, msg, args...)
+}
+
 // NotNil asserts that the specified object is not nil.
 //
 //	a.NotNil(err)