added output file integration tests

Author: arturcic

src/GitVersionExe.Tests/JsonOutputOnBuildServerTest.cs

@@ -1,6 +1,9 @@
 using System.Collections.Generic;
+using System.IO;
 using GitTools.Testing;
 using GitVersion.BuildAgents;
+using GitVersion.OutputVariables;
+using Newtonsoft.Json;
 using NUnit.Framework;
 using Shouldly;
 
@@ -41,5 +44,31 @@ public void BeingOnBuildServerWithOutputJsonDoesNotFail()
             result.OutputVariables.ShouldNotBeNull();
             result.OutputVariables.FullSemVer.ShouldBeEquivalentTo(version);
         }
+
+        [TestCase("", "GitVersion.json")]
+        [TestCase("version.json", "version.json")]
+        public void BeingOnBuildServerWithOutputJsonAndOutputFileDoesNotFail(string outputFile, string fileName)
+        {
+            using var fixture = new RemoteRepositoryFixture();
+            fixture.Repository.MakeATaggedCommit("1.2.3");
+            fixture.Repository.MakeACommit();
+
+            var env = new KeyValuePair<string, string>(TeamCity.EnvironmentVariableName, "8.0.0");
+
+            var result = GitVersionHelper.ExecuteIn(fixture.LocalRepositoryFixture.RepositoryPath, arguments: $" /output json /output buildserver /output file /outputfile {outputFile}", environments: env);
+
+            result.ExitCode.ShouldBe(0);
+            const string version = "0.1.0+4";
+            result.Output.ShouldContain($"##teamcity[buildNumber '{version}']");
+            result.OutputVariables.ShouldNotBeNull();
+            result.OutputVariables.FullSemVer.ShouldBeEquivalentTo(version);
+
+            var filePath = Path.Combine(fixture.LocalRepositoryFixture.RepositoryPath, fileName);
+            var json = File.ReadAllText(filePath);
+
+            var outputVariables = VersionVariables.FromDictionary(JsonConvert.DeserializeObject<Dictionary<string, string>>(json));
+            outputVariables.ShouldNotBeNull();
+            outputVariables.FullSemVer.ShouldBeEquivalentTo(version);
+        }
     }
 }