add throwing tests rule

Author: jqsilver

README.md

@@ -4340,6 +4340,50 @@ _You can enable the following settings in Xcode by running [this script](resourc
 
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+## Testing
+
+* <a id='prefer-throwing-tests'></a>(<a href='#prefer-throwing-tests'>link</a>) **Prefer throwing tests to `try!`** `try!` will crash your test suite like a force-unwrapped optional. XCTest and Swift Testing support throwing test methods, so use that instead. [![SwiftFormat: wrap](https://img.shields.io/badge/SwiftFormat-throwingTests-7B0051.svg)](https://github.com/nicklockwood/SwiftFormat/blob/main/Rules.md#throwingTests)
+
+  <details>
+
+  ```swift
+  import XCTest
+
+  final class SomeTestCase: XCTestCase {
+
+    // RIGHT:
+    func test_something() throws {
+      try Something().doSomething()
+    }
+
+    // WRONG:
+    func test_something() {
+      try! Something().doSomething()
+    }
+  }
+  ```
+
+  ```swift
+  import Testing
+
+  struct SomeTests {
+    // WRONG:
+    @Test
+    func something() {
+      try! Something().doSomething()
+    }
+
+    // RIGHT:
+    @Test
+    func something() throws {
+      try Something().doSomething()
+    }
+  }
+  ```
+  </details>
+
+**[⬆ back to top](#table-of-contents)**
+
 ## Contributors
 
   - [View Contributors](https://github.com/airbnb/swift/graphs/contributors)