👌 Add feature test for InternalSwitcher

tests/feature/FeatureTestCase.swift

@@ -0,0 +1,49 @@
+//
+//  FeatureTestCase.swift
+//  Feature Tests
+//
+//  Created by Nico Verbruggen on 07/11/2022.
+//  Copyright © 2022 Nico Verbruggen. All rights reserved.
+//
+
+import XCTest
+
+class FeatureTestCase: XCTestCase {
+
+    var fakeFileSystem: TestableFileSystem {
+        let fs = ActiveFileSystem.shared
+
+        if fs is TestableFileSystem {
+            return fs as! TestableFileSystem
+        }
+
+        fatalError("The active filesystem is not a TestableFileSystem. Please use `ActiveFileSystem` to use the fake filesystem.")
+    }
+
+    public func assertFileSystemHas(
+        _ path: String,
+        file: StaticString = #filePath,
+        line: UInt = #line
+    ) {
+        XCTAssertTrue(fakeFileSystem.files.keys.contains(path), file: file, line: line)
+    }
+
+    public func assertFileSystemDoesNotHave(
+        _ path: String,
+        file: StaticString = #filePath,
+        line: UInt = #line
+    ) {
+        XCTAssertFalse(fakeFileSystem.files.keys.contains(path), file: file, line: line)
+    }
+
+    public func assertFileHasContents(
+        _ path: String,
+        contents: String,
+        file: StaticString = #filePath,
+        line: UInt = #line
+    ) {
+        XCTAssertEqual(contents, fakeFileSystem.files[path]?.content, file: file, line: line)
+    }
+
+}
+