zig-testing

Use when writing or debugging Zig tests on master (0.17.0-dev), choosing a std.testing assertion, deciding between zig test file.zig and zig build test, filtering with --test-filter, tracking down a testing.allocator leak report, using testing.tmpDir or testing.io for file I/O in tests, calling refAllDecls or checkAllAllocationFailures, skipping with error.SkipZigTest, writing a test Decl {} block, reading a test…