Add mocks to json database tests

src/database/json.rs

@@ -6,9 +6,13 @@ use std::path::{Path, PathBuf};
 use serde::de::DeserializeOwned;
 use serde::Serialize;
 
+#[cfg(test)]
+use mockall::automock;
+
 use super::{Database, DatabaseRead, DatabaseWrite};
 
 /// Trait for the JSON database backend.
+#[cfg_attr(test, automock)]
 pub trait JsonDatabaseBackend {
     /// Read the JSON string from the backend.
     fn read(&self) -> Result<String, std::io::Error>;
@@ -81,25 +85,12 @@ impl JsonDatabaseBackend for JsonDatabaseFileBackend {
 
 #[cfg(test)]
 mod tests {
+    use mockall::predicate;
+
     use super::*;
 
     use crate::{tests::COLLECTION, Artist, TrackFormat};
 
-    struct JsonDatabaseTestBackend {
-        json: String,
-    }
-
-    impl JsonDatabaseBackend for JsonDatabaseTestBackend {
-        fn read(&self) -> Result<String, std::io::Error> {
-            Ok(self.json.clone())
-        }
-
-        fn write(&mut self, json: &str) -> Result<(), std::io::Error> {
-            assert_eq!(json, self.json);
-            Ok(())
-        }
-    }
-
     fn artist_to_json(artist: &Artist) -> String {
         let album_artist = &artist.id.name;
 
@@ -167,9 +158,14 @@ mod tests {
     #[test]
     fn write() {
         let write_data = COLLECTION.to_owned();
-        let backend = JsonDatabaseTestBackend {
-            json: artists_to_json(&write_data),
-        };
+        let input = artists_to_json(&write_data);
+
+        let mut backend = MockJsonDatabaseBackend::new();
+        backend
+            .expect_write()
+            .with(predicate::eq(input))
+            .times(1)
+            .return_once(|_| Ok(()));
 
         JsonDatabase::new(Box::new(backend))
             .write(&write_data)
@@ -179,9 +175,10 @@ mod tests {
     #[test]
     fn read() {
         let expected = COLLECTION.to_owned();
-        let backend = JsonDatabaseTestBackend {
-            json: artists_to_json(&expected),
-        };
+        let result = Ok(artists_to_json(&expected));
+
+        let mut backend = MockJsonDatabaseBackend::new();
+        backend.expect_read().times(1).return_once(|| result);
 
         let mut read_data: Vec<Artist> = vec![];
         JsonDatabase::new(Box::new(backend))
@@ -194,9 +191,17 @@ mod tests {
     #[test]
     fn reverse() {
         let expected = COLLECTION.to_owned();
-        let backend = JsonDatabaseTestBackend {
-            json: artists_to_json(&expected),
-        };
+        let input = artists_to_json(&expected);
+        let result = Ok(input.clone());
+
+        let mut backend = MockJsonDatabaseBackend::new();
+        backend
+            .expect_write()
+            .with(predicate::eq(input))
+            .times(1)
+            .return_once(|_| Ok(()));
+        backend.expect_read().times(1).return_once(|| result);
+
         let mut database = JsonDatabase::new(Box::new(backend));
 
         let write_data = COLLECTION.to_owned();