test(common): introduce mock util and MockInitializer trait

Author: Alenar

mithril-common/src/test_utils/mock_extensions.rs

@@ -0,0 +1,61 @@
+//! A set of tools for working with `automock`
+//!
+//! IMPORTANT: To avoid polluting production code, those tools do not expose or reexpose any
+//! `automock`types, users need to add them themselves to their crates.
+use std::sync::Arc;
+
+/// Helper to create configured Mockall mock.
+///
+/// This allows creation of the mock in a dedicated block isolated from the remaining test method
+/// code.
+pub struct MockBuilder<M: Default> {
+    phantom: std::marker::PhantomData<M>,
+}
+
+impl<M: Default> MockBuilder<M> {
+    /// Create a new instance of the mock with the given configuration
+    ///
+    /// The type must be specified either:
+    /// ```
+    /// use mithril_common::test_utils::mock_extensions::MockBuilder;
+    /// # #[derive(Default)] struct MockType {};
+    ///
+    /// // from the builder generic
+    /// let mock = MockBuilder::<MockType>::configure(|mock| {});
+    ///
+    /// // or from the closure parameter
+    /// let mock = MockBuilder::configure(|mock: &mut MockType| {});
+    /// ```
+    pub fn configure(mock_config: impl FnOnce(&mut M)) -> Arc<M> {
+        let mut mock = M::default();
+        mock_config(&mut mock);
+        Arc::new(mock)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[mockall::automock]
+    trait TestTrait {
+        fn test_method(&self) -> String;
+    }
+
+    #[test]
+    fn using_mock_builder() {
+        // specify the type on the closure parameter
+        let mock = MockBuilder::configure(|mock: &mut MockTestTrait| {
+            mock.expect_test_method()
+                .returning(|| "test explicit type".to_string());
+        });
+        assert_eq!("test explicit type".to_string(), mock.test_method());
+
+        // specify the type on the builder generic
+        let mock = MockBuilder::<MockTestTrait>::configure(|mock| {
+            mock.expect_test_method()
+                .returning(|| "test turbofish".to_string());
+        });
+        assert_eq!("test turbofish".to_string(), mock.test_method());
+    }
+}

mithril-common/src/test_utils/mod.rs

@@ -8,6 +8,7 @@
 
 pub mod fake_data;
 pub mod fake_keys;
+pub mod mock_extensions;
 
 mod cardano_transactions_builder;
 mod certificate_chain_builder;