Add runnable examples for mocking HOME and the clock - #18
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Two common testing problems get their own integration tests, each written against business code that calls the standard library directly. tests/environment.rs mocks env::var. In the 2024 edition env::set_var is unsafe, and it changes the environment of the whole test process, so tests that set variables must share a lock or run one at a time. The tests read a log level and a database URL with values chosen per thread, cover a missing variable and a default port, check that three overlapping threads each see their own value, and check that a thread without a session still finds the variable unset. The file forbids unsafe code. tests/clock.rs mocks SystemTime::now. Code that reads the clock directly usually has to take a clock parameter before a test can choose the time. The tests run a morning check at chosen instants, step across both edges of the morning window, advance the clock 20 seconds per reading so a token expires without sleeping, and check that other threads keep the machine clock. Checked locally with cargo fmt and cargo clippy --workspace --all-targets -- -D warnings on x86_64-pc-windows-msvc, and cargo clippy -- -D warnings for the two new test targets on aarch64-unknown-linux-gnu, aarch64-apple-darwin, x86_64-apple-darwin and aarch64-pc-windows-msvc. The tests run in CI.
The environment tests now follow a case that keeps breaking CI in other projects: code that shortens paths under the home directory to ~, and tests that point HOME somewhere else with the unsafe env::set_var. Parallel tests then read each other's HOME, so projects add environment locks, serialize the tests, or change the function to take the home directory as a parameter. The business code reads HOME with env::var_os and stays unchanged. The tests mock env::var_os per thread and cover a path under home, home itself, a sibling directory that shares the prefix, an unset or empty HOME, three overlapping threads that each see their own HOME, and a thread without a session that still sees the real value. The file still forbids unsafe code. The log-level and database-URL examples from the previous commit are gone. The previous commit's tests passed CI on all seven jobs (run 34743354785). Checked this change locally with cargo fmt and cargo clippy -- -D warnings for the environment test target on x86_64-pc-windows-msvc, aarch64-unknown-linux-gnu, aarch64-apple-darwin, x86_64-apple-darwin and aarch64-pc-windows-msvc.
The HOME and clock scenarios are meant to be read on their own and linked to, so they now live in examples/environment.rs and examples/clock.rs. Each file keeps its business code at the top, adds a main that runs that code without mocks, and holds its tests in a cfg(test) module. Cargo builds examples during cargo test but runs their tests only when the example is declared with test = true, so Cargo.toml declares both. CI's cargo test --workspace and cargo clippy --all-targets therefore run and lint them in all seven required jobs. tests/examples.rs fails if a file in examples/ has no such entry, so a new example cannot drop out of CI unnoticed. The coverage gate already ignored test files; it now ignores examples/ too, because an example's main never runs under cargo llvm-cov and is not library code. The package include list gains examples/**, which tests/examples.rs reads.
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Adds two runnable examples with tests:
examples/environment.rs: tests code that readsHOMEby mockingenv::var_osper thread, withoutset_var.examples/clock.rs: tests time-based code by mockingSystemTime::now, without sleeping.Both are declared with
test = true, so CI runs their tests.tests/examples.rsfails if a new example is missing that setting. The coverage gate ignoresexamples/.