Comment and tests

Sources/General/KingfisherManager.swift

@@ -50,6 +50,15 @@ public struct RetrieveImageResult {
     /// `originalSource` will be kept as the initial `source` which issued the image loading process.
     public let originalSource: Source
     
+    /// Gets the data behind the result.
+    ///
+    /// If this result is from a network downloading (when `cacheType == .none`), calling this returns the downloaded
+    /// data. If the reuslt is from cache, it serializes the image with the given cache serializer in the loading option
+    /// and returns the result.
+    ///
+    /// - Note:
+    /// This can be a time-consuming action, so if you need to use the data for multiple times, it is suggested to hold
+    /// it and prevent keeping calling this too frequently.
     public let data: () -> Data?
 }
 

Tests/KingfisherTests/KingfisherManagerTests.swift

@@ -1073,6 +1073,62 @@ class KingfisherManagerTests: XCTestCase {
             }
         waitForExpectations(timeout: 1.0)
     }
+    
+    func testImageResultContainsDataWhenDownloaded() {
+        let exp = expectation(description: #function)
+        let url = testURLs[0]
+        stub(url, data: testImageData)
+        
+        manager.retrieveImage(with: url) { result in
+            XCTAssertNotNil(result.value?.data())
+            XCTAssertEqual(result.value!.data(), testImageData)
+            XCTAssertEqual(result.value!.cacheType, .none)
+            exp.fulfill()
+        }
+        
+        waitForExpectations(timeout: 3, handler: nil)
+    }
+    
+    func testImageResultContainsDataWhenLoadFromMemoryCache() {
+        let exp = expectation(description: #function)
+        let url = testURLs[0]
+        stub(url, data: testImageData)
+
+        manager.retrieveImage(with: url) { _ in
+            self.manager.retrieveImage(with: url) { result in
+                XCTAssertEqual(result.value!.cacheType, .memory)
+                XCTAssertNotNil(result.value?.data())
+                XCTAssertEqual(
+                    result.value!.data(),
+                    DefaultCacheSerializer.default.data(with: result.value!.image, original: nil)
+                )
+                exp.fulfill()
+            }
+        }
+        
+        waitForExpectations(timeout: 3, handler: nil)
+    }
+    
+    func testImageResultContainsDataWhenLoadFromDiskCache() {
+        let exp = expectation(description: #function)
+        let url = testURLs[0]
+        stub(url, data: testImageData)
+
+        manager.retrieveImage(with: url) { _ in
+            self.manager.cache.clearMemoryCache()
+            self.manager.retrieveImage(with: url) { result in
+                XCTAssertEqual(result.value!.cacheType, .disk)
+                XCTAssertNotNil(result.value?.data())
+                XCTAssertEqual(
+                    result.value!.data(),
+                    DefaultCacheSerializer.default.data(with: result.value!.image, original: nil)
+                )
+                exp.fulfill()
+            }
+        }
+        
+        waitForExpectations(timeout: 3, handler: nil)
+    }
 }
 
 class SimpleProcessor: ImageProcessor {