Running Tests

In this guide, code examples are often given as runnable tests. Before proceeding, make sure that you can run them successfully.

Success

Save the following text as test_pass.zig, and run zig test test_pass.zig; you should read All 1 tests passed. in your terminal.

const std = @import("std");
const expect = std.testing.expect;

test "always succeeds" {
    try expect(true);
}

note

Some code examples in this guide will have their imports at the top hidden, make sure to get them by clicking the copy button on the top-right of the code block.

Try the same test without the try keyword. What happened?

Failure

Now, save the following text as test_fail.zig and observe it fail.

const std = @import("std");
const expect = std.testing.expect;

test "always fails" {
    try expect(false);
}

Which should output something like:

Test [1/1] test.always fails... FAIL (TestUnexpectedResult)
/usr/lib/zig/std/testing.zig:515:14: 0x2241ef in expect (test)
    if (!ok) return error.TestUnexpectedResult;
             ^
[...]/test_fail:5:5: 0x224305 in test.always fails (test)
    try expect(false);
    ^
0 passed; 0 skipped; 1 failed.