add a build test

src/cli/test/roc_subcommands.zig

@@ -420,3 +420,122 @@ test "roc test/str/app.roc runs successfully" {
     // 1. Command succeeded (zero exit code)
     try testing.expect(result.term == .Exited and result.term.Exited == 0);
 }
+
+// =============================================================================
+// roc build tests
+// =============================================================================
+
+test "roc build creates executable from test/int/app.roc" {
+    const testing = std.testing;
+    const gpa = testing.allocator;
+
+    // Create a temp directory for the output
+    var tmp_dir = testing.tmpDir(.{});
+    defer tmp_dir.cleanup();
+
+    const tmp_path = try tmp_dir.dir.realpathAlloc(gpa, ".");
+    defer gpa.free(tmp_path);
+
+    const output_path = try std.fs.path.join(gpa, &.{ tmp_path, "test_app" });
+    defer gpa.free(output_path);
+
+    const output_arg = try std.fmt.allocPrint(gpa, "--output={s}", .{output_path});
+    defer gpa.free(output_arg);
+
+    const result = try util.runRoc(gpa, &.{ "build", output_arg }, "test/int/app.roc");
+    defer gpa.free(result.stdout);
+    defer gpa.free(result.stderr);
+
+    // Verify that:
+    // 1. Command succeeded (zero exit code)
+    try testing.expect(result.term == .Exited and result.term.Exited == 0);
+
+    // 2. Output file was created
+    const stat = tmp_dir.dir.statFile("test_app") catch |err| {
+        std.debug.print("Failed to stat output file: {}\nstderr: {s}\n", .{ err, result.stderr });
+        return err;
+    };
+
+    // 3. Output file is executable (non-zero size)
+    try testing.expect(stat.size > 0);
+}
+
+test "roc build executable runs correctly" {
+    const testing = std.testing;
+    const gpa = testing.allocator;
+
+    // Create a temp directory for the output
+    var tmp_dir = testing.tmpDir(.{});
+    defer tmp_dir.cleanup();
+
+    const tmp_path = try tmp_dir.dir.realpathAlloc(gpa, ".");
+    defer gpa.free(tmp_path);
+
+    const output_path = try std.fs.path.join(gpa, &.{ tmp_path, "test_app" });
+    defer gpa.free(output_path);
+
+    const output_arg = try std.fmt.allocPrint(gpa, "--output={s}", .{output_path});
+    defer gpa.free(output_arg);
+
+    // Build the app
+    const build_result = try util.runRoc(gpa, &.{ "build", output_arg }, "test/int/app.roc");
+    defer gpa.free(build_result.stdout);
+    defer gpa.free(build_result.stderr);
+
+    try testing.expect(build_result.term == .Exited and build_result.term.Exited == 0);
+
+    // Run the built executable
+    const run_result = try std.process.Child.run(.{
+        .allocator = gpa,
+        .argv = &.{output_path},
+        .max_output_bytes = 10 * 1024 * 1024,
+    });
+    defer gpa.free(run_result.stdout);
+    defer gpa.free(run_result.stderr);
+
+    // Verify that:
+    // 1. Executable ran successfully
+    try testing.expect(run_result.term == .Exited and run_result.term.Exited == 0);
+
+    // 2. Output contains expected success message
+    const has_success = std.mem.indexOf(u8, run_result.stdout, "SUCCESS") != null or
+        std.mem.indexOf(u8, run_result.stdout, "PASSED") != null;
+    try testing.expect(has_success);
+}
+
+test "roc build fails with file not found error" {
+    const testing = std.testing;
+    const gpa = testing.allocator;
+
+    const result = try util.runRoc(gpa, &.{"build"}, "nonexistent_file.roc");
+    defer gpa.free(result.stdout);
+    defer gpa.free(result.stderr);
+
+    // Verify that:
+    // 1. Command failed (non-zero exit code)
+    try testing.expect(result.term != .Exited or result.term.Exited != 0);
+
+    // 2. Stderr contains file not found error
+    const has_error = std.mem.indexOf(u8, result.stderr, "FileNotFound") != null or
+        std.mem.indexOf(u8, result.stderr, "not found") != null or
+        std.mem.indexOf(u8, result.stderr, "Failed") != null;
+    try testing.expect(has_error);
+}
+
+test "roc build fails with invalid target error" {
+    const testing = std.testing;
+    const gpa = testing.allocator;
+
+    const result = try util.runRoc(gpa, &.{ "build", "--target=invalid_target_name" }, "test/int/app.roc");
+    defer gpa.free(result.stdout);
+    defer gpa.free(result.stderr);
+
+    // Verify that:
+    // 1. Command failed (non-zero exit code)
+    try testing.expect(result.term != .Exited or result.term.Exited != 0);
+
+    // 2. Stderr contains invalid target error
+    const has_error = std.mem.indexOf(u8, result.stderr, "Invalid target") != null or
+        std.mem.indexOf(u8, result.stderr, "invalid") != null;
+    try testing.expect(has_error);
+}