issue#97 - Stream depending on params for S3.getObject

index.js

@@ -164,6 +164,9 @@ function mockServiceMethod(service, client, method, replace) {
         return promise;
       } : undefined,
       createReadStream: function() {
+        if (storedResult instanceof Readable) {
+          return storedResult;
+        }
         if (replace instanceof Readable) {
           return replace;
         } else {
@@ -204,7 +207,7 @@ function mockServiceMethod(service, client, method, replace) {
     if (typeof replace === 'function') {
       const result = replace.apply(replace, userArgs.concat([callback]));
       if (storedResult === undefined && result != null &&
-          typeof result.then === 'function') {
+          (typeof result.then === 'function' || result instanceof Readable)) {
         storedResult = result
       }
     }

test/index.test.js

@@ -245,6 +245,19 @@ test('AWS.mock function should mock AWS service and method on the service', func
       st.end();
     }));
   });
+  t.test('request object createReadStream works with returned streams', function(st) {
+    awsMock.mock('S3', 'getObject', () => {
+      const bodyStream = new Readable();
+      bodyStream.push('body');
+      bodyStream.push(null);
+      return bodyStream;
+    });
+    const stream = new AWS.S3().getObject('getObject').createReadStream();
+    stream.pipe(concatStream(function(actual) {
+      st.equals(actual.toString(), 'body');
+      st.end();
+    }));
+  });
   t.test('request object createReadStream works with strings', function(st) {
     awsMock.mock('S3', 'getObject', 'body');
     const s3 = new AWS.S3();