Write a test

Let's write a test to see if what we wrote is working.

Run tests from main.zig

To run this test with

zig build test

we must add a section to our main.zig module:

///////////////////////////////////////////////////////////////////////////////
//
//                              Tests
//
///////////////////////////////////////////////////////////////////////////////

comptime {
    if (builtin.is_test) {
        _ = @import("Editor.zig");
    }
}

In fact, our build.zig is set up in a way that running zig build test executes the tests that are in main.zig. When tests are executed from a module, all tests placed in imported modules are executed too.

We don't want any test in main.zig, but with this comptime block we import the modules we want to test, if builtin.is_test is true, and this happens only when we're running tests.

Importing these modules will cause their tests to be executed, which is what we want.

Add the test in Editor

You should add some constants in Editor:

const linux = @import("linux.zig");

const mem = std.mem;
const expect = std.testing.expect;

Then we add a test to src/Editor.zig. Add the test section just above the Constants section.

///////////////////////////////////////////////////////////////////////////////
//
//                              Tests
//
///////////////////////////////////////////////////////////////////////////////

test "insert rows" {
    var da = std.heap.DebugAllocator(.{}){};
    defer _ = da.deinit();

    var e = try t.Editor.init(da.allocator(), .{ .rows = 50, .cols = 180 });
    try e.openFile("src/main.zig");
    defer e.deinit();

    const row = e.rowAt(6).chars.items;
    try expect(mem.eql(u8, "pub fn main() !void {", row));
}

It's a simple test that verifies the number of rows that have been read, and that the content of one row actually matches the one in the file.

I initialize the editor with a 'fake' screen, because this isn't an interactive terminal. Also, we avoid the event loop by reading directly the file with openFile(), otherwise processKeypress() would hang the test.

If we modify main.zig again, this test could fail, or course. I will not, but maybe you will.