Fixes the issue with fn test and adds relevant test cases, fixes #650 (#651)

* Fixes the issue with fn test and adds relevant test cases, fixes #650
* Checking log size for invalid function
* Testing the invalid function logs a few time beforr quitting
* Disabling the test for now, linked to issue #653

test/tests/test_function_test/errhello.js

@@ -0,0 +1,7 @@
+// This file has an error on purpose; async is replaced with aasync
+module.exports = aasync function(context) {
+    return {
+        status: 200,
+        body: "Hello, Fission!\n"
+    };
+}

test/tests/test_function_test/hello.js

@@ -0,0 +1,6 @@
+module.exports = async function (context) {
+    return {
+        status: 200,
+        body: "Hello, Fission!\n"
+    };
+}

test/tests/test_function_test/test_fn_test.sh

@@ -0,0 +1,68 @@
+#!/bin/bash
+
+#test:disabled
+# Disabled because CI Fails for invalid function https://github.com/fission/fission/issues/653
+
+set -euo pipefail
+
+env=nodejs-$(date +%N)
+valid_fn_name=hello-$(date +%N)
+invalid_fn_name=errhello-$(date +%N)
+
+function cleanup {
+    log "Cleaning up"
+    fission env delete --name $env
+    fission fn delete --name $valid_fn_name
+    fission fn delete --name $invalid_fn_name
+}
+
+log "Creating env $env"
+fission env create --name $env --image fission/node-env
+trap cleanup EXIT
+
+log "Creating valid function $valid_fn_name"
+fission fn create --name $valid_fn_name --env $env --code hello.js
+
+log "Testing valid function $valid_fn_name"
+fission fn test --name $valid_fn_name > /tmp/valid.log
+
+log "---Valid Function logs---"
+cat /tmp/valid.log
+log "------"
+valid_num=$(grep 'Hello, Fission' /tmp/valid.log | wc -l)
+
+if [ $valid_num -ne 1 ]
+then
+    log "Valid function Test Failed: expected 1, found $valid_num logs"
+    exit 1
+fi
+
+log "Creating function with an error $invalid_fn_name"
+fission fn create --name $invalid_fn_name --env $env --code errhello.js
+
+log "Testing invalid function $valid_fn_name"
+fission fn test --name $invalid_fn_name > /tmp/invalid.log
+
+for i in {1..10}
+do
+    size=$(wc -c </tmp/invalid.log)
+    if [ $size == 0 ]
+    then
+        fission fn test --name $invalid_fn_name > /tmp/invalid.log
+    else
+        break
+    fi
+done
+
+log "---Invalid Function logs---"
+cat /tmp/invalid.log
+log "------"
+invalid_num=$(grep 'SyntaxError' /tmp/invalid.log | wc -l)
+
+if [ $invalid_num -ne 1 ]
+then
+    log "Invalid function Failed: expected 1, found $invalid_num logs"
+    exit 1
+fi
+
+log "All tests passed"