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.Tobject as the first argument. This is how it writes the errors out through the normalgo testcapabilities. - 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)
}
}
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 setup 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)
// setup 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)
// setup 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)
}
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
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))
}
Reference
- https://github.com/stretchr/testify
- https://pkg.go.dev/github.com/stretchr/testify
- https://github.com/vektra/mockery