WIP add integration test notes

Tests/CodegenIntegrationTests/Tests/mergedSourceFromDefinitionRootNeedsFullyQualifedName/README.MD

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+# Overview
+
+
+
+## Reference Issue: https://github.com/apollographql/apollo-ios/pull/3120
+
+## Solution
+
+All properties that are lists of scalars should use the `_setScalarList` function when initialized inside mock objects.

Tests/CodegenIntegrationTests/Tests/mergedSourceFromDefinitionRootNeedsFullyQualifedName/operation.graphql

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+fragment Test on Event {
+  child {
+    ... on ChildA {
+      innerChild: child {
+        foo
+      }
+    }
+  }
+  ... on EventA {
+    bar
+  }
+  ... on EventB {
+    baz
+  }
+}

Tests/CodegenIntegrationTests/Tests/mergedSourceFromDefinitionRootNeedsFullyQualifedName/schema.graphqls

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+type Query {
+  test: Event!
+}
+
+interface Event {
+  child: Child!
+}
+
+type EventA implements Event {
+  child: Child!
+  bar: String!
+}
+
+type EventB implements Event {
+  child: Child!
+  baz: String!
+}
+
+interface Child {
+  foo: String!
+  child: Child
+}
+
+type ChildA implements Child {
+  foo: String!
+  child: Child
+}