package com.proxerme.library.util;

import android.support.test.InstrumentationRegistry;

import com.proxerme.library.connection.ProxerConnection;

import org.junit.After;
import org.junit.Before;

import java.io.IOException;

import okhttp3.mockwebserver.MockWebServer;

/**
 * Base class for all {@link com.proxerme.library.connection.ProxerRequest} subclass tests.
 *
 * @author Ruben Gees
 */
public class RequestTest {

    protected MockWebServer server;
    protected ProxerConnection connection;

    protected RequestTest() {

    }

    @Before
    public void setUp() throws IOException {
        server = new MockWebServer();
        connection = new ProxerConnection.Builder("test",
                InstrumentationRegistry.getContext()).build();

        server.start();
    }

    @After
    public void tearDown() throws IOException {
        server.shutdown();
    }
}

package com.proxerme.library.util;

import android.support.test.InstrumentationRegistry;

import com.proxerme.library.connection.ProxerConnection;

import org.junit.AfterClass;
import org.junit.BeforeClass;

import java.io.IOException;

import okhttp3.mockwebserver.MockWebServer;

/**
 * Base class for all {@link com.proxerme.library.connection.ProxerRequest} subclass tests.
 *
 * @author Ruben Gees
 */
public class RequestTest {

    protected static MockWebServer server = new MockWebServer();
    protected static ProxerConnection connection = new ProxerConnection.Builder("test",
            InstrumentationRegistry.getContext()).build();

    protected RequestTest() {

    }

    @BeforeClass
    public static void setUpServer() throws IOException {
        server.start();
    }

    @AfterClass
    public static void tearDownServer() throws IOException {
        server.shutdown();
    }
}

--- 
+++ 
@@ -4,8 +4,8 @@
 
 import com.proxerme.library.connection.ProxerConnection;
 
-import org.junit.AfterClass;
-import org.junit.BeforeClass;
+import org.junit.After;
+import org.junit.Before;
 
 import java.io.IOException;
 
@@ -18,21 +18,24 @@
  */
 public class RequestTest {
 
-    protected static MockWebServer server = new MockWebServer();
-    protected static ProxerConnection connection = new ProxerConnection.Builder("test",
-            InstrumentationRegistry.getContext()).build();
+    protected MockWebServer server;
+    protected ProxerConnection connection;
 
     protected RequestTest() {
 
     }
 
-    @BeforeClass
-    public static void setUpServer() throws IOException {
+    @Before
+    public void setUp() throws IOException {
+        server = new MockWebServer();
+        connection = new ProxerConnection.Builder("test",
+                InstrumentationRegistry.getContext()).build();
+
         server.start();
     }
 
-    @AfterClass
-    public static void tearDownServer() throws IOException {
+    @After
+    public void tearDown() throws IOException {
         server.shutdown();
     }
 }
Fix tests by constructing a new server and connection in setup
