zig/test/standalone/child_process/build.zig

const std = @import("std");
const builtin = @import("builtin");

pub fn build(b: *std.Build) void {
    const test_step = b.step("test", "Test it");
    b.default_step = test_step;

    const optimize: std.builtin.OptimizeMode = .Debug;
    const target: std.zig.CrossTarget = .{};

    if (builtin.os.tag == .wasi) return;

    const child = b.addExecutable(.{
        .name = "child",
        .root_source_file = .{ .path = "child.zig" },
        .optimize = optimize,
        .target = target,
    });

    const main = b.addExecutable(.{
        .name = "main",
        .root_source_file = .{ .path = "main.zig" },
        .optimize = optimize,
        .target = target,
    });
    const run = b.addRunArtifact(main);
    run.addArtifactArg(child);
    run.expectExitCode(0);

    test_step.dependOn(&run.step);
}