ci: add GitHub Actions matrix for Bazel support

.github/workflows/ci.yml

@@ -0,0 +1,42 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: bazel ${{ matrix.bazel }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          - macos-latest
+        bazel:
+          - 9.0.1
+          - 9.0.2
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v4
+
+      - name: Set up Bazelisk
+        uses: bazelbuild/setup-bazelisk@v3
+
+      - name: Select Bazel version
+        run: echo "USE_BAZEL_VERSION=${{ matrix.bazel }}" >> "$GITHUB_ENV"
+
+      - name: Show Bazel version
+        run: bazel version
+
+      - name: Run test suite
+        run: bazel test //...

README.md

@@ -6,13 +6,30 @@ Bazel rules for building [Zig](https://ziglang.org/) projects.
 
 - `zig_binary` — compile Zig source files into an executable
 - `zig_library` — compile Zig source files into a static library (`.a`)
+- `zig_test` — compile and run Zig tests with `bazel test`
 - Bazel toolchain integration with platform-aware compiler resolution
 
 ## Requirements
 
 - Zig: 0.13.0
 - Bazel: 9.0+
 
+## CI and support matrix
+
+The repository currently runs CI on:
+
+- Bazel 9.0.1 on Linux and macOS
+- Bazel 9.0.2 on Linux and macOS
+
+This gives us coverage for the minimum supported Bazel 9 line and a newer Bazel 9 patch release that is currently available on GitHub-hosted runners.
+
+CI currently runs:
+
+- `bazel build //...`
+- `bazel test ...` when Bazel test targets are present
+
+As the ruleset grows, this matrix can expand to include more Bazel versions, additional examples, and stricter validation.
+
 ## Setup
 
 ### Bzlmod (MODULE.bazel)
@@ -79,3 +96,24 @@ zig_library(
 |-----------|-------------|----------|
 | `srcs` | List of `.zig` source files | Yes |
 | `main` | Root source file for the library. Defaults to the first file in `srcs`. | No |
+
+### `zig_test` example
+
+Compiles and runs Zig tests through `bazel test`.
+
+```starlark
+load("@rules_zig//zig:defs.bzl", "zig_test")
+
+zig_test(
+    name = "math_test",
+    srcs = [
+        "math_test.zig",
+        "math.zig",
+    ],
+)
+```
+
+| Attribute | Description | Required |
+|-----------|-------------|----------|
+| `srcs` | List of `.zig` source files needed by the test, including imported sibling files | Yes |
+| `main` | Root test source file. Defaults to the first file in `srcs`. | No |

examples/math_lib/BUILD.bazel

@@ -1,6 +1,14 @@
-load("//zig:defs.bzl", "zig_library")
+load("//zig:defs.bzl", "zig_library", "zig_test")
 
 zig_library(
     name = "math",
     srcs = ["math.zig"],
 )
+
+zig_test(
+    name = "math_test",
+    srcs = [
+        "math_test.zig",
+        "math.zig",
+    ],
+)

examples/math_lib/math_test.zig

@@ -0,0 +1,8 @@
+const std = @import("std");
+const math = @import("math.zig");
+
+test "basic arithmetic helpers" {
+    try std.testing.expectEqual(@as(i32, 5), math.add(2, 3));
+    try std.testing.expectEqual(@as(i32, 6), math.multiply(2, 3));
+    try std.testing.expectEqual(@as(i32, -1), math.subtract(2, 3));
+}

zig/defs.bzl

@@ -1,6 +1,7 @@
 """Public API for rules_zig."""
 
-load("//zig:rules.bzl", _zig_binary = "zig_binary", _zig_library = "zig_library")
+load("//zig:rules.bzl", _zig_binary = "zig_binary", _zig_library = "zig_library", _zig_test = "zig_test")
 
 zig_binary = _zig_binary
 zig_library = _zig_library
+zig_test = _zig_test

zig/rules.bzl

@@ -134,3 +134,74 @@ zig_library = rule(
     },
     toolchains = ["//zig:toolchain_type"],
 )
+
+def _zig_test_impl(ctx):
+    zig_toolchain = ctx.toolchains["//zig:toolchain_type"]
+    zig_info = zig_toolchain.zig_info
+    zig_exe = zig_info.zig_exe
+
+    srcs = ctx.files.srcs
+    if len(srcs) == 0:
+        fail("zig_test requires at least one source file in srcs.")
+
+    main_filename = ctx.attr.main if ctx.attr.main else srcs[0].basename
+    main_src = None
+    for src in srcs:
+        if src.basename == main_filename or src.short_path.endswith(main_filename):
+            main_src = src
+            break
+    if not main_src:
+        fail("main file '{}' not found in srcs.".format(main_filename))
+
+    out = ctx.actions.declare_file(ctx.label.name)
+    src_tree = ctx.actions.declare_directory(ctx.label.name + "_srcs")
+    zig_link = ctx.actions.declare_file(ctx.label.name + "_zig")
+
+    ctx.actions.symlink(
+        output = zig_link,
+        target_file = zig_exe,
+        is_executable = True,
+    )
+
+    copy_commands = []
+    for src in srcs:
+        copy_commands.append("cp '{}' '{}/{}'".format(src.path, src_tree.path, src.basename))
+
+    command = "set -euo pipefail\nROOT=\"$PWD\"\nmkdir -p '{src_tree}'\n{copies}\ncd '{src_tree}'\n\"$ROOT/{zig}\" test '{main}' -femit-bin=\"$ROOT/{out}\" --cache-dir /tmp/zig-cache --global-cache-dir /tmp/zig-global-cache".format(
+        src_tree = src_tree.path,
+        copies = "\n".join(copy_commands),
+        zig = zig_link.path,
+        main = main_src.basename,
+        out = out.path,
+    )
+
+    ctx.actions.run_shell(
+        outputs = [out, src_tree],
+        inputs = srcs + [zig_link],
+        command = command,
+        mnemonic = "ZigCompileTest",
+        progress_message = "Compiling Zig test %{label}",
+    )
+
+    return [
+        DefaultInfo(
+            files = depset([out]),
+            executable = out,
+        ),
+    ]
+
+zig_test = rule(
+    implementation = _zig_test_impl,
+    attrs = {
+        "srcs": attr.label_list(
+            doc = "Zig test source files to compile.",
+            allow_files = [".zig"],
+            mandatory = True,
+        ),
+        "main": attr.string(
+            doc = "The root source file for the test. Defaults to the first file in srcs.",
+        ),
+    },
+    test = True,
+    toolchains = ["//zig:toolchain_type"],
+)