docs: document new lib functions & usage

docs/reference.md

@@ -0,0 +1,53 @@
+# Reference
+
+## `flakeModule`
+
+The `flakeModule` for [flake-parts](https://flake.parts).
+
+## `lib`
+
+### `module`
+
+The nix module for validation of inputs etc.
+Used internally by `mkNixtestConfig`.
+
+### `autodiscover`
+
+```nix
+autodiscover {
+  dir,
+  pattern ? ".*_test.nix",
+}
+```
+
+Finds all test files in `dir` matching `pattern`.
+Returns a list of modules (can be passed to `mkNixtest`'s `modules` arg).
+
+### `mkNixtestConfig`
+
+```nix
+mkNixtestConfig {
+  modules,
+  args ? {},
+}
+```
+
+Evaluates the test `modules`.
+`args` are passed to the modules using `_module.args = args`.
+
+**Noteworthy attributes**:
+
+- `app`: nixtest wrapper
+- `finalConfigJson`: derivation containing the tests json file
+
+### `mkNixtest`
+
+```nix
+mkNixtest {
+  modules,
+  args ? {},
+}
+```
+
+Creates the nixtest wrapper, using the tests in `modules`.
+Basically `(mkNixtestConfig <arguments>).app`.