add unitTests for string extensions

Author: lauramarson

AnimalsApp/AnimalsAppTests/ExtensionsTests/StringExtensionTests.swift

@@ -6,30 +6,22 @@
 //
 
 import XCTest
+@testable import AnimalsApp
 
 class StringExtensionTests: XCTestCase {
 
-    override func setUpWithError() throws {
-        // Put setup code here. This method is called before the invocation of each test method in the class.
+    func testIfIsEmptyExtensionReturnsNil() {
+        let emptyString = ""
+        let result = emptyString.testIfIsEmpty()
+        
+        XCTAssertNil(result)
     }
-
-    override func tearDownWithError() throws {
-        // Put teardown code here. This method is called after the invocation of each test method in the class.
-    }
-
-    func testExample() throws {
-        // This is an example of a functional test case.
-        // Use XCTAssert and related functions to verify your tests produce the correct results.
-        // Any test you write for XCTest can be annotated as throws and async.
-        // Mark your test throws to produce an unexpected failure when your test encounters an uncaught error.
-        // Mark your test async to allow awaiting for asynchronous code to complete. Check the results with assertions afterwards.
-    }
-
-    func testPerformanceExample() throws {
-        // This is an example of a performance test case.
-        self.measure {
-            // Put the code you want to measure the time of here.
-        }
+    
+    func testIfIsEmptyExtensionReturnsSelf() {
+        let string = "string"
+        let result = string.testIfIsEmpty()
+        
+        XCTAssertEqual(string, result)
     }
 
 }