Add Claude Code generated tests and CLAUDE.md.

Signed-off-by: moderation <[e-mail]>

CLAUDE.md

···
+# CLAUDE.md
+
+## Project Overview
+
+This is `rust-version-updater`, a CLI tool that recursively updates `rust-version` fields in Cargo.toml files to match the currently installed Rust version.
+
+## Build Requirements
+
+This project targets **Zig master** (tip of tree). It uses unstable standard library APIs that are not available in stable releases.
+
+Current development version: `0.16.0-dev.2368+380ea6fb5`
+
+## Commands
+
+```sh
+# Build
+zig build
+
+# Build release
+zig build -Doptimize=ReleaseFast
+
+# Run
+zig build run
+
+# Run with arguments
+zig build run -- --dry-run
+
+# Test
+zig build test
+```
+
+## Project Structure
+
+```
+.
+├── build.zig       # Build configuration
+├── build.zig.zon   # Package manifest
+└── src/
+    └── main.zig    # All application code and tests
+```
+
+## Code Patterns
+
+- Uses the new `std.Io` and `std.process` APIs from Zig master
+- Entry point is `pub fn main(init: process.Init)` (not the traditional `pub fn main() void`)
+- Buffered I/O with explicit flush calls
+- Tests are inline at the bottom of main.zig using `test` blocks
+- Memory allocation uses the provided `init.gpa` allocator
+- All allocations are paired with corresponding `defer` frees
+
+## Key Types
+
+- `Version` - Semver parsing and comparison
+- `ProcessResult` / `ProcessStatus` - Result of processing a Cargo.toml file
+- `Stats` - Tracks scanned/updated/skipped/error counts
+
+## Testing
+
+Tests cover the pure functions (`Version.parse`, `Version.isOlderThan`, `processContent`). The I/O-dependent functions are not unit tested.
+
+Run tests with: `zig build test`

build.zig

···
 
     const run_step = b.step("run", "Run the rust-version-updater");
     run_step.dependOn(&run_cmd.step);
+
+    const unit_tests = b.addTest(.{
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/main.zig"),
+            .target = target,
+            .optimize = optimize,
+        }),
+    });
+
+    const run_unit_tests = b.addRunArtifact(unit_tests);
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_unit_tests.step);
 }

src/main.zig

···
 
     return ProcessResult{ .status = .not_found, .old_version = null, .new_content = null };
 }
+
+// Tests
+
+test "Version.parse valid versions" {
+    const v1 = Version.parse("1.70.0").?;
+    try std.testing.expectEqual(@as(u32, 1), v1.major);
+    try std.testing.expectEqual(@as(u32, 70), v1.minor);
+    try std.testing.expectEqual(@as(u32, 0), v1.patch);
+
+    const v2 = Version.parse("1.84.1").?;
+    try std.testing.expectEqual(@as(u32, 1), v2.major);
+    try std.testing.expectEqual(@as(u32, 84), v2.minor);
+    try std.testing.expectEqual(@as(u32, 1), v2.patch);
+
+    // Two-part version (patch defaults to 0)
+    const v3 = Version.parse("1.70").?;
+    try std.testing.expectEqual(@as(u32, 1), v3.major);
+    try std.testing.expectEqual(@as(u32, 70), v3.minor);
+    try std.testing.expectEqual(@as(u32, 0), v3.patch);
+}
+
+test "Version.parse with whitespace and quotes" {
+    const v1 = Version.parse("  1.70.0  ").?;
+    try std.testing.expectEqual(@as(u32, 1), v1.major);
+    try std.testing.expectEqual(@as(u32, 70), v1.minor);
+
+    const v2 = Version.parse("\"1.84.0\"").?;
+    try std.testing.expectEqual(@as(u32, 1), v2.major);
+    try std.testing.expectEqual(@as(u32, 84), v2.minor);
+}
+
+test "Version.parse invalid versions" {
+    try std.testing.expectEqual(@as(?Version, null), Version.parse(""));
+    try std.testing.expectEqual(@as(?Version, null), Version.parse("abc"));
+    try std.testing.expectEqual(@as(?Version, null), Version.parse("1"));
+    try std.testing.expectEqual(@as(?Version, null), Version.parse("1.x.0"));
+}
+
+test "Version.isOlderThan" {
+    const v1_70 = Version{ .major = 1, .minor = 70, .patch = 0 };
+    const v1_84 = Version{ .major = 1, .minor = 84, .patch = 0 };
+    const v1_84_1 = Version{ .major = 1, .minor = 84, .patch = 1 };
+    const v2_0 = Version{ .major = 2, .minor = 0, .patch = 0 };
+
+    try std.testing.expect(v1_70.isOlderThan(v1_84));
+    try std.testing.expect(!v1_84.isOlderThan(v1_70));
+    try std.testing.expect(!v1_84.isOlderThan(v1_84)); // equal
+    try std.testing.expect(v1_84.isOlderThan(v1_84_1));
+    try std.testing.expect(v1_84_1.isOlderThan(v2_0));
+}
+
+test "processContent updates older version" {
+    const content = "[package]\nrust-version = \"1.70.0\"\n";
+    const current = Version{ .major = 1, .minor = 84, .patch = 0 };
+
+    const result = try processContent(std.testing.allocator, content, current);
+    defer if (result.new_content) |nc| std.testing.allocator.free(nc);
+
+    try std.testing.expectEqual(ProcessStatus.updated, result.status);
+    try std.testing.expectEqualStrings("1.70.0", result.old_version.?);
+    try std.testing.expectEqualStrings("[package]\nrust-version = \"1.84.0\"\n", result.new_content.?);
+}
+
+test "processContent skips newer version" {
+    const content = "[package]\nrust-version = \"1.84.0\"\n";
+    const current = Version{ .major = 1, .minor = 70, .patch = 0 };
+
+    const result = try processContent(std.testing.allocator, content, current);
+
+    try std.testing.expectEqual(ProcessStatus.skipped_not_older, result.status);
+    try std.testing.expectEqual(@as(?[]u8, null), result.new_content);
+}
+
+test "processContent skips equal version" {
+    const content = "[package]\nrust-version = \"1.84.0\"\n";
+    const current = Version{ .major = 1, .minor = 84, .patch = 0 };
+
+    const result = try processContent(std.testing.allocator, content, current);
+
+    try std.testing.expectEqual(ProcessStatus.skipped_not_older, result.status);
+}
+
+test "processContent skips workspace inheritance" {
+    const content = "[package]\nrust-version = { workspace = true }\n";
+    const current = Version{ .major = 1, .minor = 84, .patch = 0 };
+
+    const result = try processContent(std.testing.allocator, content, current);
+
+    try std.testing.expectEqual(ProcessStatus.skipped_non_semver, result.status);
+}
+
+test "processContent not found" {
+    const content = "[package]\nname = \"foo\"\nversion = \"0.1.0\"\n";
+    const current = Version{ .major = 1, .minor = 84, .patch = 0 };
+
+    const result = try processContent(std.testing.allocator, content, current);
+
+    try std.testing.expectEqual(ProcessStatus.not_found, result.status);
+}
+
+test "processContent preserves surrounding content" {
+    const content =
+        \\[package]
+        \\name = "myapp"
+        \\version = "0.1.0"
+        \\rust-version = "1.70.0"
+        \\edition = "2021"
+        \\
+        \\[dependencies]
+        \\serde = "1.0"
+        \\
+    ;
+    const current = Version{ .major = 1, .minor = 84, .patch = 0 };
+
+    const result = try processContent(std.testing.allocator, content, current);
+    defer if (result.new_content) |nc| std.testing.allocator.free(nc);
+
+    try std.testing.expectEqual(ProcessStatus.updated, result.status);
+
+    const expected =
+        \\[package]
+        \\name = "myapp"
+        \\version = "0.1.0"
+        \\rust-version = "1.84.0"
+        \\edition = "2021"
+        \\
+        \\[dependencies]
+        \\serde = "1.0"
+        \\
+    ;
+    try std.testing.expectEqualStrings(expected, result.new_content.?);
+}