E2E tests for the @actions/artifact package (#421)

* End-to-end artifact tests

* E2E tests for artifact package

scripts/test-artifact-file.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+path="$1"
+expectedContent="$2"
+
+if [ "$path" == "" ]; then
+    echo "File path not provided"
+    exit 1
+fi
+
+if [ "$expectedContent" == "" ]; then
+    echo "Expected file contents not provided"
+    exit 1
+fi
+
+if [ ! -f "$path" ]; then
+    echo "Expected file $path does not exist"
+    exit 1
+fi
+
+actualContent=$(cat $path)
+if [ "$actualContent" != "$expectedContent" ];then
+    echo "File contents are not correct, expected $expectedContent, recieved $actualContent"
+    exit 1
+fi