Writing tests in Go

Unit tests in Go are run using the go test command. To create unit tests in go to check functions, add a file with the same name as the original and add a suffix “_test”

E.g.

lrucache
|- cache.go
|- cache_test.go

To test function Foo your test name should be of the form:

func TestFoo(*testing.T)

Even if a function is not exported, and starts with a lowercase, you need to start it with an uppercase in the test function or it is not run by the go test command. When I first started go, I wrote a small piece of code that have one exported function and when I wrote the test for it. I ran it and I got a “no tests to run” warning. Then I noticed the Golang doc states:

func TestXxx(*testing.T) 
where Xxx does not start with a lowercase letter.  

E.g. Test for function findNumber

func TestFindNumber(t *testing.T) {
    result := findNumber([]int{5, 3, 1})
    expected := 2
    if result != expected {
        t.Error("Incorrect result Expected ", expected, "Got:", result)
    }

}

Test tables

We can use anonymous structs to write very clear table tests that have multiple inputs and expected results without relying on any external package. E.g.

var testTable = []struct { 
    isdev    bool 
    expected string 
}{ 
   {true, "/Users/"}, 
   {false, "/home/httpd/"}, 
} 
for _, test := range testTable { 
    config.IsDev = test.isdev 
    actual := getUsersHomeDir() 
    if !strings.Contains(actual, test.expected) {                t.Errorf("getUsersHomeDir: Expected %s, Got %s", 
test.expected, actual) 
   } 
} 

Test options

Here are some very useful go test options

//Run Verbose 
go test -v 
//run tests with race detector
go test -race

This is a neat trick, I used to test multiple packages in a repo and exclude one or more folders. go list will only include folders with .go files in them. I had functional tests in a folder called test-client written in Go that I wanted to exclude.

go test `go list ./... | grep -v test-client`

Also check out the post Mocking with Golang so you could write unit tests that rely on external dependencies like servers. Using interfaces these can be simulated to write tests without actually accessing the external resource.

Reference Links

• Examples in the test code