Adds tests

.github/workflows/ci.yml

@@ -17,3 +17,5 @@ jobs:
       run: cargo fmt --check
     - name: Lint
       run: cargo clippy -- -D warnings
+    - name: Run tests
+      run: cargo test --workspace

Cargo.toml

@@ -7,3 +7,6 @@ repository = "https://github.com/ultimaweapon/erdp"
 edition = "2021"
 
 [dependencies]
+
+[dev-dependencies]
+thiserror = "1.0.58"

src/lib.rs

@@ -35,3 +35,33 @@ impl<'a> std::fmt::Display for Display<'a> {
         Ok(())
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use thiserror::Error;
+
+    #[test]
+    fn single() {
+        let e = TestError::Single;
+
+        assert_eq!(e.display().to_string(), "an error without nested errors");
+    }
+
+    #[test]
+    fn nested() {
+        let e = std::io::Error::from(std::io::ErrorKind::NotFound);
+        let e = TestError::Nested(e);
+
+        assert_eq!(e.display().to_string(), "nested error -> entity not found");
+    }
+
+    #[derive(Debug, Error)]
+    enum TestError {
+        #[error("an error without nested errors")]
+        Single,
+
+        #[error("nested error")]
+        Nested(#[source] std::io::Error),
+    }
+}