update setup method to correctly create new system for testing every test

test/testHelpers/apolloTestServerHelpers.ts

@@ -19,6 +19,17 @@ function setUpTestServer() {
   });
 }
 
+const systemInfoForTesting = {
+  id: "1", name: "Chapman University", passioSystemId: "263"
+};
+
+export function buildSystemForTesting() {
+  return InterchangeSystem.build(
+    systemInfoForTesting,
+    new InMemoryNotificationRepository()
+  );
+}
+
 /**
  * Returns a `ServerContext` object which can be passed to requests
  * for testing.
@@ -26,18 +37,11 @@ function setUpTestServer() {
 export function setupTestServerContext() {
   const context: { [key: string] : any } = {};
 
-  const systems = [
-    InterchangeSystem.build(
-      {
-        id: "1", name: "Chapman University", passioSystemId: "263"
-      },
-      new InMemoryNotificationRepository()
-    ),
-  ]
-
   beforeEach(() => {
-    context.systems = systems;
-    context.findSystemById = (_: string) => systems[0];
+    context.systems = [
+      buildSystemForTesting(),
+    ];
+    context.findSystemById = (_: string) => context.systems[0];
   });
 
   return context as ServerContext;