# Go Testing #

Go includes a testing package that works with the `go test` command.

Create a test file with a name ending in `_test.go`.
The `_test.go` file should contain functions named like `TestMyfunc` with the signature:

	func TestMyfunc(t *testing.T)

If the test function calls a failure function like `t.Error` or `t.Fail`, Go considers the test failed.

For a package named `stringutil` with a `Reverse` function, create a `stringutil_test.go` file:

	package stringutil
	import "testing"
	func TestReverse(t *testing.T) {
		cases := []struct {
			in, want string
		}{
			{"Hello, world", "dlrow ,olleH"},
			{"Hello, 世界", "界世 ,olleH"},
			{"", ""},
		}
		for _, c := range cases {
			got := Reverse(c.in)
			if got != c.want {
				t.Errorf("Reverse(%q) == %q, want %q", c.in, got, c.want)
			}
		}
	}

...and run the test:

	$ go test example.com/stringutil

See how much of the project we've covered with tests:

	$ go test -cover

## Table-Driven Tests ##

A commonly used pattern is table-driven tests.
Supply a struct matching inputs with expected return values.

	func TestFib(t *testing.T) {
		tests := []struct {
			input int
			want  int
		}{
			{1, 1},
			{2, 1},
			{3, 2},
			{4, 3},
			{5, 5},
			{6, 8},
			{7, 13},
		}
		for _, test := range tests {
			got := Fib(test.input)
			if got != test.want {
				t.Errorf("Fib(%d) got %d, want %d", test.input, got, test.want)
			}
		}
	}

## Testing Main ##

What if the project is too small to break into different packages?
How do we test main?

	$ ls
	main.go     main_test.go
	$ go test *.go
	ok      command-line-arguments  0.003s

## Links ##

- https://golang.org/pkg/testing/
- https://talks.golang.org/2014/testing.slide#1
- https://stackoverflow.com/questions/31352239/how-to-test-the-main-package-functions-in-golang

Sun Oct  1 11:43:57 EDT 2017