Go by Example: Testing

Unit testing is an important part of writing principled Go programs. The `testing` package provides the tools we need to write unit tests and the `go test` command runs tests.
For the sake of demonstration, this code is in package `main`, but it could be any package. Testing code typically lives in the same package as the code it tests.	package main
	import ( "fmt" "testing" )
We’ll be testing this simple implementation of an integer minimum. Typically, the code we’re testing would be in a source file named something like `intutils.go`, and the test file for it would then be named `intutils_test.go`.	func IntMin(a, b int) int { if a < b { return a } return b }
A test is created by writing a function with a name beginning with `Test`.	func TestIntMinBasic(t *testing.T) { ans := IntMin(2, -2) if ans != -2 {
`t.Error` will report test failures but continue executing the test. `t.Fatal` will report test failures and stop the test immediately.	t.Errorf("IntMin(2, -2) = %d; want -2", ans) } }
Writing tests can be repetitive, so it’s idiomatic to use a table-driven style, where test inputs and expected outputs are listed in a table and a single loop walks over them and performs the test logic.	func TestIntMinTableDriven(t *testing.T) { var tests = []struct { a, b int want int }{ {0, 1, 0}, {1, 0, 0}, {2, -2, -2}, {0, -1, -1}, {-1, 0, -1}, }
t.Run enables running “subtests”, one for each table entry. These are shown separately when executing `go test -v`.	for _, tt := range tests {
	testname := fmt.Sprintf("%d,%d", tt.a, tt.b) t.Run(testname, func(t *testing.T) { ans := IntMin(tt.a, tt.b) if ans != tt.want { t.Errorf("got %d, want %d", ans, tt.want) } }) } }
	func BenchmarkIntMin(b *testing.B) { for i := 0; i < b.N; i++ { IntMin(1, 2) } }

Run all tests in the current project in verbose mode.

$ go test -v
== RUN   TestIntMinBasic
--- PASS: TestIntMinBasic (0.00s)
=== RUN   TestIntMinTableDriven
=== RUN   TestIntMinTableDriven/0,1
=== RUN   TestIntMinTableDriven/1,0
=== RUN   TestIntMinTableDriven/2,-2
=== RUN   TestIntMinTableDriven/0,-1
=== RUN   TestIntMinTableDriven/-1,0
--- PASS: TestIntMinTableDriven (0.00s)
    --- PASS: TestIntMinTableDriven/0,1 (0.00s)
    --- PASS: TestIntMinTableDriven/1,0 (0.00s)
    --- PASS: TestIntMinTableDriven/2,-2 (0.00s)
    --- PASS: TestIntMinTableDriven/0,-1 (0.00s)
    --- PASS: TestIntMinTableDriven/-1,0 (0.00s)
PASS
ok      examples/testing    0.023s

Next example: Command-Line Arguments.