Custom Zig Test Runner

test_runner.zig

// in your build.zig, you can specify a custom test runner:
// const tests = b.addTest(.{
//   .target = target,
//   .optimize = optimize,
//   .test_runner = "test_runner.zig", // add this line
//   .root_source_file = .{ .path = "src/main.zig" },
// });

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

const Allocator = std.mem.Allocator;

const BORDER = "=" ** 80;

// use in custom panic handler
var current_test: ?[]const u8 = null;

pub fn main() !void {
    var mem: [4096]u8 = undefined;
    var fba = std.heap.FixedBufferAllocator.init(&mem);

    const allocator = fba.allocator();

    const env = Env.init(allocator);
    defer env.deinit(allocator);

    var slowest = SlowTracker.init(allocator, 5);
    defer slowest.deinit();

    var pass: usize = 0;
    var fail: usize = 0;
    var skip: usize = 0;
    var leak: usize = 0;

    const printer = Printer.init();
    printer.fmt("\r\x1b[0K", .{}); // beginning of line and clear to end of line

    for (builtin.test_functions) |t| {
        std.testing.allocator_instance = .{};
        var status = Status.pass;
        slowest.startTiming();

        const is_unnamed_test = std.mem.endsWith(u8, t.name, ".test_0");
        if (env.filter) |f| {
            if (!is_unnamed_test and std.mem.indexOf(u8, t.name, f) == null) {
                continue;
            }
        }

        const friendly_name = blk: {
            const name = t.name;
            var it = std.mem.splitScalar(u8, name, '.');
            while (it.next()) |value| {
                if (std.mem.eql(u8, value, "test")) {
                    const rest = it.rest();
                    break :blk if (rest.len > 0) rest else name;
                    }
            }
            break :blk name;
        };

        current_test = friendly_name;
        const result = t.func();
        current_test = null;

        if (is_unnamed_test) {
            continue;
        }

        const ns_taken = slowest.endTiming(friendly_name);

        if (std.testing.allocator_instance.deinit() == .leak) {
            leak += 1;
            printer.status(.fail, "\n{s}\n\"{s}\" - Memory Leak\n{s}\n", .{BORDER, friendly_name, BORDER});
        }

        if (result) |_| {
            pass += 1;
        } else |err| switch (err) {
            error.SkipZigTest => {
                skip += 1;
                status = .skip;
            },
            else => {
                status = .fail;
                fail += 1;
                printer.status(.fail, "\n{s}\n\"{s}\" - {s}\n{s}\n", .{BORDER, friendly_name, @errorName(err), BORDER});
                if (@errorReturnTrace()) |trace| {
                    std.debug.dumpStackTrace(trace.*);
                }
                if (env.fail_first) {
                    break;
                }
            }
        }

        if (env.verbose) {
            const ms = @as(f64, @floatFromInt(ns_taken)) / 100_000.0;
            printer.status(status, "{s} ({d:.2}ms)\n", .{friendly_name, ms});
        } else {
            printer.status(status, ".", .{});
        }
    }

    const total_tests = pass + fail;
    const status = if (fail == 0) Status.pass else Status.fail;
    printer.status(status, "\n{d} of {d} test{s} passed\n", .{pass, total_tests, if (total_tests != 1) "s" else ""});
    if (skip > 0) {
        printer.status(.skip, "{d} test{s} skipped\n", .{skip, if (skip != 1) "s" else ""});
    }
    if (leak > 0) {
        printer.status(.fail, "{d} test{s} leaked\n", .{leak, if (leak != 1) "s" else ""});
    }
    printer.fmt("\n", .{});
    try slowest.display(printer);
    printer.fmt("\n", .{});
    std.posix.exit(if (fail == 0) 0 else 1);
}

const Printer = struct {
    out: std.fs.File.Writer,

    fn init() Printer {
        return .{
            .out = std.io.getStdErr().writer(),
        };
    }

    fn fmt(self: Printer, comptime format: []const u8, args: anytype) void {
        std.fmt.format(self.out, format, args) catch unreachable;
    }

    fn status(self: Printer, s: Status, comptime format: []const u8, args: anytype) void {
        const color = switch (s) {
            .pass => "\x1b[32m",
            .fail => "\x1b[31m",
            .skip => "\x1b[33m",
            else => "",
        };
        const out = self.out;
        out.writeAll(color) catch @panic("writeAll failed?!");
        std.fmt.format(out, format, args) catch @panic("std.fmt.format failed?!");
        self.fmt("\x1b[0m", .{});
    }
};

const Status = enum {
    pass,
    fail,
    skip,
    text,
};

const SlowTracker = struct {
        const SlowestQueue = std.PriorityDequeue(TestInfo, void, compareTiming);
        max: usize,
        slowest: SlowestQueue,
        timer: std.time.Timer,

        fn init(allocator: Allocator, count: u32) SlowTracker {
                const timer = std.time.Timer.start() catch @panic("failed to start timer");
                var slowest = SlowestQueue.init(allocator, {});
                slowest.ensureTotalCapacity(count) catch @panic("OOM");
                return .{
                        .max = count,
                        .timer = timer,
                        .slowest = slowest,
                };
        }

        const TestInfo = struct {
                ns: u64,
                name: []const u8,
        };

        fn deinit(self: SlowTracker) void {
                self.slowest.deinit();
        }

        fn startTiming(self: *SlowTracker) void {
            self.timer.reset();
        }

        fn endTiming(self: *SlowTracker, test_name: []const u8) u64 {
                var timer = self.timer;
                const ns = timer.lap();

                var slowest = &self.slowest;

                if (slowest.count() < self.max) {
                        // Capacity is fixed to the # of slow tests we want to track
                        // If we've tracked fewer tests than this capacity, than always add
                        slowest.add(TestInfo{ .ns = ns, .name = test_name }) catch @panic("failed to track test timing");
                        return ns;
                }

                {
                        // Optimization to avoid shifting the dequeue for the common case
                        // where the test isn't one of our slowest.
                        const fastest_of_the_slow = slowest.peekMin() orelse unreachable;
                        if (fastest_of_the_slow.ns > ns) {
                                // the test was faster than our fastest slow test, don't add
                                return ns;
                        }
                }

                // the previous fastest of our slow tests, has been pushed off.
                _ = slowest.removeMin();
                slowest.add(TestInfo{ .ns = ns, .name = test_name }) catch @panic("failed to track test timing");
                return ns;
        }

        fn display(self: *SlowTracker, printer: Printer) !void {
                var slowest = self.slowest;
                const count = slowest.count();
                printer.fmt("Slowest {d} test{s}: \n", .{count, if (count != 1) "s" else ""});
                while (slowest.removeMinOrNull()) |info| {
                        const ms = @as(f64, @floatFromInt(info.ns)) / 100_000.0;
                        printer.fmt("  {d:.2}ms\t{s}\n", .{ms, info.name});
                }
        }

        fn compareTiming(context: void, a: TestInfo, b: TestInfo) std.math.Order {
                _ = context;
                return std.math.order(a.ns, b.ns);
        }
};

const Env = struct {
    verbose: bool,
    fail_first: bool,
    filter: ?[]const u8,

    fn init(allocator: Allocator) Env {
        return .{
            .verbose = readEnvBool(allocator, "TEST_VERBOSE", true),
            .fail_first = readEnvBool(allocator, "TEST_FAIL_FIRST", false),
            .filter = readEnv(allocator, "TEST_FILTER"),
        };
    }

    fn deinit(self: Env, allocator: Allocator) void {
        if (self.filter) |f| {
            allocator.free(f);
        }
    }

    fn readEnv(allocator: Allocator, key: []const u8) ?[]const u8 {
        const v = std.process.getEnvVarOwned(allocator, key) catch |err| {
            if (err == error.EnvironmentVariableNotFound) {
                    return null;
            }
            std.log.warn("failed to get env var {s} due to err {}", .{key, err});
            return null;
        };
        return v;
    }

    fn readEnvBool(allocator: Allocator, key: []const u8, deflt: bool) bool {
        const value = readEnv(allocator, key) orelse return deflt;
        defer allocator.free(value);
        return std.ascii.eqlIgnoreCase(value, "true");
    }
};

pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace, ret_addr: ?usize) noreturn {
    if (current_test) |ct| {
        std.debug.print("\x1b[31m{s}\npanic running \"{s}\"\n{s}\x1b[0m\n", .{BORDER, ct, BORDER});
    }
    std.builtin.default_panic(msg, error_return_trace, ret_addr);
}