Add test build with just command

build.zig

@@ -31,4 +31,26 @@ pub fn build(b: *std.Build) void {
 
     const run_step = b.step("run", "run the game");
     run_step.dependOn(&run_cmd.step);
+
+    // test step (doesn't need raylib)
+    const test_step = b.step("test", "run unit tests");
+
+    const test_files = [_][]const u8{
+        "src/fixed.zig",
+        "src/trig.zig",
+        "src/terrain.zig",
+        "src/game.zig",
+    };
+
+    for (test_files) |file| {
+        const unit_test = b.addTest(.{
+            .root_module = b.createModule(.{
+                .root_source_file = b.path(file),
+                .target = target,
+                .optimize = optimize,
+            }),
+        });
+        const run_test = b.addRunArtifact(unit_test);
+        test_step.dependOn(&run_test.step);
+    }
 }

justfile

@@ -34,3 +34,6 @@ clean:
 # check for compile errors without building
 check:
     zig build --summary all 2>&1 | head -50
+
+test:
+    zig build test