Basic tests for PictureCache (#19)

* update: move PictureCache to another file

* update: add couple of tests for PictureCache

* update: remove playground

* resolve: review threads

Sources/Picture/Public/PictureCache.swift

@@ -0,0 +1,23 @@
+import SwiftUI
+
+public class PictureCache {
+    private var cache: [URL: Image]
+    private var lock: NSLock
+
+    public init() {
+        cache = [:]
+        lock = NSLock()
+    }
+
+    public func `get`(url: URL) -> Image? {
+        lock.lock(); defer { lock.unlock() }
+
+        return cache[url]
+    }
+
+    public func `set`(value: Image?, for url: URL) {
+        lock.lock(); defer { lock.unlock() }
+
+        cache[url] = value
+    }
+}

Sources/Picture/Public/PictureSource.swift

@@ -1,27 +1,5 @@
 import SwiftUI
 
-public class PictureCache {
-    private var cache: [URL: Image]
-    private var lock: NSLock
-
-    public init() {
-        cache = [:]
-        lock = NSLock()
-    }
-
-    public func `get`(url: URL) -> Image? {
-        lock.lock(); defer { lock.unlock() }
-
-        return cache[url]
-    }
-
-    public func `set`(value: Image?, for url: URL) {
-        lock.lock(); defer { lock.unlock() }
-
-        cache[url] = value
-    }
-}
-
 public enum PictureSource {
     public private(set) static var cache: PictureCache = PictureCache()
 

Tests/PictureTests/PictureCacheTests.swift

@@ -0,0 +1,27 @@
+import XCTest
+import SwiftUI
+@testable import Picture
+
+final class PictureCacheTests: XCTestCase {
+  private let faviconURL: URL = .init(string: "https://openbytes.com/favicon.png")!
+
+  internal func testNotFoundImageForSpecifiedURL() {
+    let cache = PictureCache()
+
+    let image = cache.get(url: faviconURL)
+
+    XCTAssertNil(image)
+  }
+
+  internal func testFoundImageForSpecifiedURL() {
+    let cache = PictureCache()
+
+    let expectedImage = Image("house")
+
+    cache.set(value: expectedImage, for: faviconURL)
+
+    let actualImage = cache.get(url: faviconURL)
+
+    XCTAssertEqual(actualImage, expectedImage)
+  }
+}