Testify - Thou Shalt Write Tests

[!NOTE] Testify is being maintained at v1, no breaking changes will be accepted in this repo.
See discussion about v2.

Go code (golang) set of packages that provide many tools for testifying that your code will behave as you intend.

Features include:

• Easy assertions
• Mocking
• Testing suite interfaces and functions

Get started:

• Install testify with one line of code, or update it with another
• For an introduction to writing test code in Go, see https://go.dev/doc/code#Testing
• Check out the API Documentation https://pkg.go.dev/github.com/stretchr/testify
• Use testifylint (via golanci-lint) to avoid common mistakes
• A little about Test-Driven Development (TDD)

assert package

The assert package provides some helpful methods that allow you to write better test code in Go.

• Prints friendly, easy to read failure descriptions
• Allows for very readable code
• Optionally annotate each assertion with a message

See it in action:

package yours

import (
  "testing"
  "github.com/stretchr/testify/assert"
)

func TestSomething(t *testing.T) {

  // assert equality
  assert.Equal(t, 123, 123, "they should be equal")

  // assert inequality
  assert.NotEqual(t, 123, 456, "they should not be equal")

  // assert for nil (good for errors)
  assert.Nil(t, object)

  // assert for not nil (good when you expect something)
  if assert.NotNil(t, object) {

    // now we know that object isn't nil, we are safe to make
    // further assertions without causing any errors
    assert.Equal(t, "Something", object.Value)

  }

}

• Every assert func takes the testing.T object as the first argument. This is how it writes the errors out through the normal go test capabilities.
• Every assert func returns a bool indicating whether the assertion was successful or not, this is useful for if you want to go on making further assertions under certain conditions.

if you assert many times, use the below:

package yours

import (
  "testing"
  "github.com/stretchr/testify/assert"
)

func TestSomething(t *testing.T) {
  assert := assert.New(t)

  // assert equality
  assert.Equal(123, 123, "they should be equal")

  // assert inequality
  assert.NotEqual(123, 456, "they should not be equal")

  // assert for nil (good for errors)
  assert.Nil(object)

  // assert for not nil (good when you expect something)
  if assert.NotNil(object) {

    // now we know that object isn't nil, we are safe to make
    // further assertions without causing any errors
    assert.Equal("Something", object.Value)
  }
}

require package

The require package provides same global functions as the assert package, but instead of returning a boolean result they terminate current test. These functions must be called from the goroutine running the test or benchmark function, not from other goroutines created during the test. Otherwise race conditions may occur.

See t.FailNow for details.

mock package

The mock package provides a mechanism for easily writing mock objects that can be used in place of real objects when writing test code.

An example test function that tests a piece of code that relies on an external object testObj, can set up expectations (testify) and assert that they indeed happened:

package yours

import (
  "testing"
  "github.com/stretchr/testify/mock"
)

/*
  Test objects
*/

// MyMockedObject is a mocked object that implements an interface
// that describes an object that the code I am testing relies on.
type MyMockedObject struct{
  mock.Mock
}

// DoSomething is a method on MyMockedObject that implements some interface
// and just records the activity, and returns what the Mock object tells it to.
//
// In the real object, this method would do something useful, but since this
// is a mocked object - we're just going to stub it out.
//
// NOTE: This method is not being tested here, code that uses this object is.
func (m *MyMockedObject) DoSomething(number int) (bool, error) {

  args := m.Called(number)
  return args.Bool(0), args.Error(1)

}

/*
  Actual test functions
*/

// TestSomething is an example of how to use our test object to
// make assertions about some target code we are testing.
func TestSomething(t *testing.T) {

  // create an instance of our test object
  testObj := new(MyMockedObject)

  // set up expectations
  testObj.On("DoSomething", 123).Return(true, nil)

  // call the code we are testing
  targetFuncThatDoesSomethingWithObj(testObj)

  // assert that the expectations were met
  testObj.AssertExpectations(t)


}

// TestSomethingWithPlaceholder is a second example of how to use our test object to
// make assertions about some target code we are testing.
// This time using a placeholder. Placeholders might be used when the
// data being passed in is normally dynamically generated and cannot be
// predicted beforehand (eg. containing hashes that are time sensitive)
func TestSomethingWithPlaceholder(t *testing.T) {

  // create an instance of our test object
  testObj := new(MyMockedObject)

  // set up expectations with a placeholder in the argument list
  testObj.On("DoSomething", mock.Anything).Return(true, nil)

  // call the code we are testing
  targetFuncThatDoesSomethingWithObj(testObj)

  // assert that the expectations were met
  testObj.AssertExpectations(t)


}

// TestSomethingElse2 is a third example that shows how you can use
// the Unset method to cleanup handlers and then add new ones.
func TestSomethingElse2(t *testing.T) {

  // create an instance of our test object
  testObj := new(MyMockedObject)

  // set up expectations with a placeholder in the argument list
  mockCall := testObj.On("DoSomething", mock.Anything).Return(true, nil)

  // call the code we are testing
  targetFuncThatDoesSomethingWithObj(testObj)

  // assert that the expectations were met
  testObj.AssertExpectations(t)

  // remove the handler now so we can add another one that takes precedence
  mockCall.Unset()

  // return false now instead of true
  testObj.On("DoSomething", mock.Anything).Return(false, nil)

  testObj.AssertExpectations(t)
}

For more information on how to write mock code, check out the API documentation for the mock package.

You can use the mockery tool to autogenerate the mock code against an interface as well, making using mocks much quicker.

suite package

[!WARNING] The suite package does not support parallel tests. See #934.

The suite package provides functionality that you might be used to from more common object-oriented languages. With it, you can build a testing suite as a struct, build setup/teardown methods and testing methods on your struct, and run them with 'go test' as per normal.

An example suite is shown below:

// Basic imports
import (
    "testing"
    "github.com/stretchr/testify/assert"
    "github.com/stretchr/testify/suite"
)

// Define the suite, and absorb the built-in basic suite
// functionality from testify - including a T() method which
// returns the current testing context
type ExampleTestSuite struct {
    suite.Suite
    VariableThatShouldStartAtFive int
}

// Make sure that VariableThatShouldStartAtFive is set to five
// before each test
func (suite *ExampleTestSuite) SetupTest() {
    suite.VariableThatShouldStartAtFive = 5
}

// All methods that begin with "Test" are run as tests within a
// suite.
func (suite *ExampleTestSuite) TestExample() {
    assert.Equal(suite.T(), 5, suite.VariableThatShouldStartAtFive)
}

// In order for 'go test' to run this suite, we need to create
// a normal test function and pass our suite to suite.Run
func TestExampleTestSuite(t *testing.T) {
    suite.Run(t, new(ExampleTestSuite))
}

For a more complete example, using all of the functionality provided by the suite package, look at our example testing suite

For more information on writing suites, check out the API documentation for the suite package.

Suite object has assertion methods:

// Basic imports
import (
    "testing"
    "github.com/stretchr/testify/suite"
)

// Define the suite, and absorb the built-in basic suite
// functionality from testify - including assertion methods.
type ExampleTestSuite struct {
    suite.Suite
    VariableThatShouldStartAtFive int
}

// Make sure that VariableThatShouldStartAtFive is set to five
// before each test
func (suite *ExampleTestSuite) SetupTest() {
    suite.VariableThatShouldStartAtFive = 5
}

// All methods that begin with "Test" are run as tests within a
// suite.
func (suite *ExampleTestSuite) TestExample() {
    suite.Equal(suite.VariableThatShouldStartAtFive, 5)
}

// In order for 'go test' to run this suite, we need to create
// a normal test function and pass our suite to suite.Run
func TestExampleTestSuite(t *testing.T) {
    suite.Run(t, new(ExampleTestSuite))
}

Installation

To install Testify, use go get:

go get github.com/stretchr/testify

This will then make the following packages available to you:

github.com/stretchr/testify/assert
github.com/stretchr/testify/require
github.com/stretchr/testify/mock
github.com/stretchr/testify/suite
github.com/stretchr/testify/http (deprecated)

Import the testify/assert package into your code using this template:

package yours

import (
  "testing"
  "github.com/stretchr/testify/assert"
)

func TestSomething(t *testing.T) {

  assert.True(t, true, "True is true!")

}

Staying up to date

To update Testify to the latest version, use go get -u github.com/stretchr/testify.

Supported go versions

We currently support the most recent major Go versions from 1.19 onward.

Contributing

Please feel free to submit issues, fork the repository and send pull requests!

When submitting an issue, we ask that you please include a complete test function that demonstrates the issue. Extra credit for those using Testify to write the test code that demonstrates it.

Code generation is used. Look for Code generated with at the top of some files. Run go generate ./... to update generated files.

We also chat on the Gophers Slack group in the #testify and #testify-dev channels.

License

This project is licensed under the terms of the MIT license.