Enabled ubuntu at appveyor

Author: stesee

PostScriptValidatorTest/PostScriptValidatorTest.cs

@@ -1,4 +1,3 @@
-using System.IO;
 using NUnit.Framework;
 
 namespace Tests
@@ -14,6 +13,7 @@ public void ShouldDetectCompliantPostscript()
                 Assert.True(result);
             }
         }
+
         [Test]
         public void ShouldDetectNonCompliantPostscript()
         {
@@ -23,6 +23,7 @@ public void ShouldDetectNonCompliantPostscript()
                 Assert.False(result);
             }
         }
+
         [Test]
         public void ShouldNotFailOnMultipleDisposeCalls()
         {
@@ -31,5 +32,13 @@ public void ShouldNotFailOnMultipleDisposeCalls()
             postscriptValidator.Dispose();
             postscriptValidator.Dispose();
         }
+
+        [Test]
+        public void ShouldNotFailOnMultipleDisposeWithoutEvenUsingOnceCalls()
+        {
+            var postscriptValidator = new PostScriptValidator.PostScriptValidator();
+            postscriptValidator.Dispose();
+            postscriptValidator.Dispose();
+        }
     }
 }

appveyor.yml

@@ -1,15 +1,9 @@
 version: 1.0.{build}
-image: Visual Studio 2019
+image:
+  - Visual Studio 2019
+  - Ubuntu
 skip_tags: true
-branches:
-  only:
-  - master
 configuration: Release
-before_build:
-- ps: >-
-    nuget restore
-
-    . "C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.7.2 Tools\x64\sn.exe" -k ./PostScriptValidator/PostScriptValidator.snk
 build:
   project: PostScriptValidator.sln
   verbosity: minimal