test bindings in an integration-tests crate

integration-tests/README.md

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+# Integration Tests for Taskchampion
+
+## "Regular" Tests
+
+Some of the tests in `tests/` are just regular integration tests.
+Nothing exciting to see.
+
+## Bindings Tests
+
+The bindings tests are a bit more interesting, since they are written in C.
+They are composed of a collection of "suites", each in one C file in `integration-tests/src/bindings_tests/`.
+Each suite contains a number of tests (using [Unity](http://www.throwtheswitch.org/unity)) and an exported function named after the suite that returns an exit status (1 = failure).
+
+The build script (`integration-tests/build.rs`) builds these files into a library that is linked with the `integration_tests` library crate.
+This crate contains a `bindings_tests` module with a pub function for each suite.
+
+Finally, the `integration-tests/tests/bindings.rs` test file calls each of those functions in a separate test case.
+
+### Adding Tests
+
+To add a test, select a suite and add a new test-case function.
+Add a `RUN_TEST` invocation for your new function to the `.._tests` function at the bottom.
+Keep the `RUN_TEST`s in the same order as the functions they call.
+
+### Adding Suites
+
+To add a suite,
+
+1. Add a new C file in `integration-tests/src/bindings_tests/`.
+1. Add a new `.file(..)` to build that file in `integration-tests/build.rs`.
+1. Add a `suite!(..)` to `integration-tests/src/bindings_tests/mod.rs`.
+1. Add a `suite!(..)` to `integration-tests/tests/bindings.rs`.