panic: add .Panic() to mock.Call

Panic mocks a function call that panics with th specfied message

mock/mock.go

@@ -65,6 +65,11 @@ type Call struct {
 	// reference. It's useful when mocking methods such as unmarshalers or
 	// decoders.
 	RunFn func(Arguments)
+
+	// PanicMsg holds msg to be used to mock panic on the function call
+	//  if the PanicMsg is set to a non nil string the function call will panic
+	// irrespective of other settings
+	PanicMsg *string
 }
 
 func newCall(parent *Mock, methodName string, callerInfo []string, methodArguments ...interface{}) *Call {
@@ -77,6 +82,7 @@ func newCall(parent *Mock, methodName string, callerInfo []string, methodArgumen
 		Repeatability:   0,
 		WaitFor:         nil,
 		RunFn:           nil,
+		PanicMsg:        nil,
 	}
 }
 
@@ -100,6 +106,18 @@ func (c *Call) Return(returnArguments ...interface{}) *Call {
 	return c
 }
 
+// Panic specifies if the functon call should fail and the panic message
+//
+//    Mock.On("DoSomething").Panic("test panic")
+func (c *Call) Panic(msg string) *Call {
+	c.lock()
+	defer c.unlock()
+
+	c.PanicMsg = &msg
+
+	return c
+}
+
 // Once indicates that that the mock should only return the value once.
 //
 //    Mock.On("MyMethod", arg1, arg2).Return(returnArg1, returnArg2).Once()
@@ -392,6 +410,13 @@ func (m *Mock) MethodCalled(methodName string, arguments ...interface{}) Argumen
 		time.Sleep(call.waitTime)
 	}
 
+	m.mutex.Lock()
+	panicMsg := call.PanicMsg
+	m.mutex.Unlock()
+	if panicMsg != nil {
+		panic(*panicMsg)
+	}
+
 	m.mutex.Lock()
 	runFn := call.RunFn
 	m.mutex.Unlock()

mock/mock_test.go

@@ -486,6 +486,29 @@ func Test_Mock_Return(t *testing.T) {
 	assert.Nil(t, call.WaitFor)
 }
 
+func Test_Mock_Panic(t *testing.T) {
+
+	// make a test impl object
+	var mockedService = new(TestExampleImplementation)
+
+	c := mockedService.
+		On("TheExampleMethod", "A", "B", true).
+		Panic("panic message for example method")
+
+	require.Equal(t, []*Call{c}, mockedService.ExpectedCalls)
+
+	call := mockedService.ExpectedCalls[0]
+
+	assert.Equal(t, "TheExampleMethod", call.Method)
+	assert.Equal(t, "A", call.Arguments[0])
+	assert.Equal(t, "B", call.Arguments[1])
+	assert.Equal(t, true, call.Arguments[2])
+	assert.Equal(t, 0, call.Repeatability)
+	assert.Equal(t, 0, call.Repeatability)
+	assert.Equal(t, "panic message for example method", *call.PanicMsg)
+	assert.Nil(t, call.WaitFor)
+}
+
 func Test_Mock_Return_WaitUntil(t *testing.T) {
 
 	// make a test impl object
@@ -1420,6 +1443,14 @@ func Test_MockMethodCalled(t *testing.T) {
 	m.AssertExpectations(t)
 }
 
+func Test_MockMethodCalled_Panic(t *testing.T) {
+	m := new(Mock)
+	m.On("foo", "hello").Panic("world panics")
+
+	require.PanicsWithValue(t, "world panics", func() { m.MethodCalled("foo", "hello") })
+	m.AssertExpectations(t)
+}
+
 // Test to validate fix for racy concurrent call access in MethodCalled()
 func Test_MockReturnAndCalledConcurrent(t *testing.T) {
 	iterations := 1000