feat: tests

AGENTS.md

@@ -25,6 +25,22 @@ Alternatively, you can use Docker for a containerized environment:
 docker-compose up --build
 ```
 
+## Writing Tests
+
+All tests are written using the go standard library and are table driven.
+In this application no libraries like testify are used. Mocks are written in
+the test file using this schema:
+
+```go
+type Mock struct {
+	Foo func (string) string
+}
+
+func (m Mock) Foo(in string) string {
+	return m.Foo(in)
+}
+```
+
 ## Running Tests
 
 To run all tests for the project, use the following command: