fix issue #76, add additional create(FileSystem) within SourcePersisterFactory, some unit tests for SourcePersister (#77)

filesystem/src/main/java/com/nytimes/android/external/fs/SourcePersister.java

@@ -29,7 +29,7 @@ public class SourcePersister implements Persister<BufferedSource> {
 
     @Inject
     public SourcePersister(FileSystem fileSystem) {
-        this.sourceFileReader = new SourceFileReader(fileSystem);
+        sourceFileReader = new SourceFileReader(fileSystem);
         sourceFileWriter = new SourceFileWriter(fileSystem);
     }
 

filesystem/src/main/java/com/nytimes/android/external/fs/SourcePersisterFactory.java

@@ -2,6 +2,7 @@ package com.nytimes.android.external.fs;
 
 import android.support.annotation.NonNull;
 
+import com.nytimes.android.external.fs.filesystem.FileSystem;
 import com.nytimes.android.external.fs.filesystem.FileSystemFactory;
 import com.nytimes.android.external.store.base.Persister;
 
@@ -31,4 +32,18 @@ public final class SourcePersisterFactory {
         }
         return new SourcePersister(FileSystemFactory.create(root));
     }
+
+    /**
+     * Returns a new {@link BufferedSource} persister with the provided fileSystem as the root of the
+     * persistence {@link com.nytimes.android.external.fs.filesystem.FileSystem}.
+     *
+     * @throws IOException
+     */
+    @NonNull
+    public static Persister<BufferedSource> create(@NonNull FileSystem fileSystem) throws IOException {
+        if (fileSystem == null) {
+            throw new IllegalArgumentException("fileSystem cannot be null.");
+        }
+        return new SourcePersister(fileSystem);
+    }
 }

filesystem/src/test/java/com/nytimes/android/external/fs/SourcePersisterTest.java

@@ -0,0 +1,69 @@
+package com.nytimes.android.external.fs;
+
+import com.nytimes.android.external.fs.filesystem.FileSystem;
+import com.nytimes.android.external.store.base.impl.BarCode;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.NoSuchElementException;
+
+import okio.BufferedSource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+
+public class SourcePersisterTest {
+
+    @Rule
+    public ExpectedException expectedException = ExpectedException.none();
+
+    @Mock
+    FileSystem fileSystem;
+    @Mock
+    BufferedSource bufferedSource;
+
+    private SourcePersister sourcePersister;
+    private final BarCode simple = new BarCode("type", "key");
+
+    @Before
+    public void setUp() {
+        MockitoAnnotations.initMocks(this);
+        sourcePersister = new SourcePersister(fileSystem);
+    }
+
+    @Test
+    public void readExists() throws FileNotFoundException {
+        when(fileSystem.exists(SourcePersister.pathForBarcode(simple)))
+                .thenReturn(true);
+        when(fileSystem.read(SourcePersister.pathForBarcode(simple))).thenReturn(bufferedSource);
+
+        BufferedSource returnedValue = sourcePersister.read(simple).toBlocking().single();
+        assertThat(returnedValue).isEqualTo(bufferedSource);
+    }
+
+    @Test
+    public void readDoesNotExist() throws FileNotFoundException {
+        expectedException.expect(NoSuchElementException.class);
+        when(fileSystem.exists(SourcePersister.pathForBarcode(simple)))
+                .thenReturn(false);
+
+        sourcePersister.read(simple).toBlocking().single();
+    }
+
+    @Test
+    public void write() throws IOException {
+        assertThat(sourcePersister.write(simple, bufferedSource).toBlocking().single()).isTrue();
+    }
+
+    @Test
+    public void pathForBarcode() {
+        assertThat(SourcePersister.pathForBarcode(simple)).isEqualTo("typekey");
+    }
+}