Make TestResult generic

Cargo.toml

@@ -11,3 +11,6 @@ categories = ["development-tools::testing"]
 exclude = [".github"]
 
 [dependencies]
+
+[dev-dependencies]
+rstest = "0.18.2"

src/lib.rs

@@ -29,6 +29,8 @@ impl<T: std::fmt::Display> From<T> for TestError {
 ///
 /// # Examples
 ///
+/// Using [`TestResult`] as a result of the test function:
+///
 /// ```
 /// use testresult::TestResult;
 ///
@@ -40,7 +42,31 @@ impl<T: std::fmt::Display> From<T> for TestError {
 ///     Ok(())
 /// }
 /// ```
-pub type TestResult = std::result::Result<(), TestError>;
+///
+/// As [`TestResult`] is generic one can use it in test helper functions to return
+/// objects to test functions.
+/// For example [`TestResult`] used in `rstest` fixture returns a [`std::fs::File`] object that
+/// can be used by the test:
+///
+/// ```
+/// use rstest::{fixture, rstest};
+/// use std::fs::File;
+/// use testresult::TestResult;
+///
+/// #[fixture]
+/// fn a_file() -> TestResult<File> {
+///     let file = File::open("this-file-does-not-exist")?;
+///     // ...
+///     Ok(file)
+/// }
+///
+/// #[rstest]
+/// fn it_works(file: File) -> TestResult {
+///     // ...
+///     Ok(())
+/// }
+/// ```
+pub type TestResult<T = ()> = std::result::Result<T, TestError>;
 
 #[cfg(test)]
 mod tests {
@@ -54,13 +80,15 @@ mod tests {
         Ok(())
     }
 
+    // helper function which always fails
+    fn test_fn() -> TestResult<std::fs::File> {
+        let file = std::fs::File::open("this-file-does-not-exist")?;
+        Ok(file)
+    }
+
     #[test]
     fn check_if_panics() -> TestResult {
         let result = std::panic::catch_unwind(|| {
-            fn test_fn() -> TestResult {
-                std::fs::File::open("this-file-does-not-exist")?;
-                Ok(())
-            }
             let _ = test_fn();
         });
         assert!(result.is_err());