diff --git a/EventSourceTests/EventSourceTests.swift b/EventSourceTests/EventSourceTests.swift
index ad04bee..f8e66dd 100644
--- a/EventSourceTests/EventSourceTests.swift
+++ b/EventSourceTests/EventSourceTests.swift
@@ -9,15 +9,24 @@
 import XCTest
 @testable import EventSource
 
-class EventSourceTests: XCTestCase {
+final class EventSourceTests: XCTestCase {
 
-    var eventSource: EventSource!
-    let url = URL(string: "https://localhost")!
+    private var eventSource: EventSource!
+    private var url: URL!
 
     override func setUp() {
+        super.setUp()
+
+        url = URL(string: "https://localhost")!
         eventSource = EventSource(url: url, headers: ["header": "value"])
     }
 
+    override func tearDown() {
+        eventSource = nil
+        url = nil
+        super.tearDown()
+    }
+
     func testCreation() {
         XCTAssertEqual(url, eventSource.url)
         XCTAssertEqual(eventSource.headers, ["header": "value"])
diff --git a/EventSourceTests/EventStreamParserTests.swift b/EventSourceTests/EventStreamParserTests.swift
index 7adc42e..bb2d9c5 100644
--- a/EventSourceTests/EventStreamParserTests.swift
+++ b/EventSourceTests/EventStreamParserTests.swift
@@ -10,7 +10,7 @@ import UIKit
 import XCTest
 @testable import EventSource
 
-class EventStreamParserTests: XCTestCase {
+final class EventStreamParserTests: XCTestCase {
 
     func testExtractingEvents() {
         let eventParser = EventStreamParser()
diff --git a/EventSourceTests/EventTests.swift b/EventSourceTests/EventTests.swift
index b77f79c..3fb0fc8 100644
--- a/EventSourceTests/EventTests.swift
+++ b/EventSourceTests/EventTests.swift
@@ -10,8 +10,10 @@ import UIKit
 import XCTest
 @testable import EventSource
 
-class EventTests: XCTestCase {
-    let newLineCharacters = ["\r\n", "\n", "\r"]
+final class EventTests: XCTestCase {
+    private var newLineCharacters: [String] {
+        ["\r\n", "\n", "\r"]
+    }
 
     func testIgnoreComment() {
         var event = Event(eventString: ":retry", newLineCharacters: newLineCharacters)
diff --git a/EventSourceTests/Mock/URLSessionDataTaskMock.swift b/EventSourceTests/Mock/URLSessionDataTaskMock.swift
index 6effa5c..a2eb4a7 100644
--- a/EventSourceTests/Mock/URLSessionDataTaskMock.swift
+++ b/EventSourceTests/Mock/URLSessionDataTaskMock.swift
@@ -8,7 +8,7 @@
 
 import Foundation
 
-class URLSessionDataTaskMock: URLSessionDataTask {
+final class URLSessionDataTaskMock: URLSessionDataTask {
 
     let mockResponse: URLResponse?