Update test_function docs

test/test-manager/README.me

@@ -1,13 +1,13 @@
 # Writing tests for [MullvadVPN App](https://github.com/mullvad/mullvadvpn-app/)
 
-The `test-manager` crate is where the tests for the [MullvadVPN
+The `test-manager` crate is where end-to-end tests for the [MullvadVPN
 App](https://github.com/mullvad/mullvadvpn-app/) resides. The tests are located
 in different modules under `test-manager/src/tests/`.
 
 ## Getting started
 
-Tests are regular Rust functions! Except that they are also `async` and are
-marked with the `#[test_function]` attribute
+Tests are regular Rust functions! Except that they are also `async` and marked
+with the `#[test_function]` attribute
 
 ```rust
 #[test_function]
@@ -19,8 +19,29 @@ pub async fn test(
 }
 ```
 
-A more detailed writeup on how the `#[test_function]` macro works is given as a
-doc-comment in [test_macro::lib.rs](./test_macro/src/lib.rs).
+The `test_function` macro allows you to write tests for the MullvadVPN App in a
+format which is very similiar to [standard Rust unit
+tests](https://doc.rust-lang.org/book/ch11-01-writing-tests.html). A more
+detailed writeup on how the `#[test_function]` macro works is given as a
+doc-comment in [test_macro::test_function](./test_macro/src/lib.rs).
 
 If a new module is created, make sure to add it in
 `test-manager/src/tests/mod.rs`.
+
+### UI/Graphical tests
+
+It is possible to write tests for asserting graphical properties in the app, but
+this is a slightly more involved process. GUI tests are written in `Typescript`,
+and reside in the `gui/test/e2e` folder in the app repository. Packaging of
+these tests is also done from the `gui/` folder.
+
+Assuming that a graphical test `gui-test.spec` has been bundled correctly, it
+can be invoked from any Rust function by calling
+`test_manager::tests::ui::run_test(rpc:
+.., params: ..) -> Result<ExecResult,
+Error>`
+
+```rust
+// Run a UI test. Panic if any assertion in it fails!
+test_manager::tests::ui::run_test(&rpc, &["gui-test.spec"]).await.unwrap()
+```

test/test-manager/test_macro/src/lib.rs

@@ -39,8 +39,10 @@ use syn::{AttributeArgs, Lit, Meta, NestedMeta};
 ///
 /// # Examples
 ///
-/// Create a standard test. Remember that [`test_function`] will inject `rpc`
-/// and `mullvad_client` for us.
+/// ## Create a standard test.
+///
+/// Remember that [`test_function`] will inject `rpc` and `mullvad_client` for
+/// us.
 ///
 /// ```
 /// #[test_function]
@@ -52,8 +54,10 @@ use syn::{AttributeArgs, Lit, Meta, NestedMeta};
 /// }
 /// ```
 ///
-/// Create a test which will run early in the test loop, won't perform any
-/// cleanup, must succeed and will always run.
+/// ## Create a test with custom parameters
+///
+/// This test will run early in the test loop, won't perform any cleanup, must
+/// succeed and will always run.
 ///
 /// ```
 /// #[test_function(priority = -1337, cleanup = false, must_succeed = true, always_run = true)]