Improve testing with an error method

src/abstract_tree/assignment.rs

@@ -185,6 +185,9 @@ mod tests {
             ",
         );
 
-        assert!(result.unwrap_err().is_type_check_error())
+        assert!(result.unwrap_err().is_type_check_error(&Error::TypeCheck {
+            expected: Type::String,
+            actual: Type::Integer
+        }))
     }
 }

src/abstract_tree/type_definition.rs

@@ -243,13 +243,10 @@ mod tests {
     fn simple_type_check() {
         let result = evaluate("x <bool> = 1");
 
-        assert_eq!(
-            Err(Error::TypeCheck {
+        assert!(result.unwrap_err().is_type_check_error(&Error::TypeCheck {
             expected: Type::Boolean,
             actual: Type::Integer
-            }),
-            result
-        );
+        }));
     }
 
     #[test]

src/error.rs

@@ -214,11 +214,10 @@ impl Error {
         }
     }
 
-    pub fn is_type_check_error(&self) -> bool {
+    pub fn is_type_check_error(&self, other: &Error) -> bool {
         match self {
-            Error::TypeCheck { .. } => true,
-            Error::WithContext { error, .. } => error.is_type_check_error(),
-            _ => false,
+            Error::WithContext { error, .. } => error.as_ref() == other,
+            _ => self == other,
         }
     }
 }