A couple more tests.

Author: StephenMolloy

RoslynCodeProviderTest/CSharpProviderTest.cs

@@ -17,7 +17,9 @@ public static void ClassInitialize(TestContext testContext) {
             string frameworkFolder = Path.GetDirectoryName(typeof(object).Assembly.Location);
             string compilerPath = Path.Combine(frameworkFolder, "csc.exe");
             var codeDomProviderType = typeof(Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider);
+#pragma warning disable CS0618
             csharpCodeProvider = new CSharpCodeProvider(compilerSettings: CompilerSettingsHelper.CSC);
+#pragma warning restore CS0618
             AppContext.SetSwitch("Switch.System.DisableTempFileCollectionDirectoryFeature", true);
         }
 

RoslynCodeProviderTest/ProviderOptionsTests.cs

@@ -44,6 +44,32 @@ public void DefaultSettings()
             Assert.AreEqual<string>("bar2", opts.AllOptions["AnotherCoolSetting"]);
         }
 
+        [TestMethod]
+        public void FromShortConstructor()
+        {
+            IProviderOptions opts = new ProviderOptions(@"D:\My\Fun\Compiler\Path\compiles.exe", 123);
+            Assert.IsNotNull(opts);
+            Assert.AreEqual<string>(@"D:\My\Fun\Compiler\Path\compiles.exe", opts.CompilerFullPath);   // Would include csc.exe or vbc.exe if the extension we searched for wasn't fake.
+            Assert.AreEqual<int>(123, opts.CompilerServerTimeToLive);   // 10 in Production. 900 in a "dev" environment.
+            Assert.IsFalse(opts.UseAspNetSettings);  // Default via constructor is false.
+            Assert.IsFalse(opts.WarnAsError);
+            Assert.IsNull(opts.CompilerVersion);
+            Assert.AreEqual<int>(0, opts.AllOptions.Count);
+        }
+
+        [TestMethod]
+        public void FromICompilerSettings()
+        {
+            IProviderOptions opts = new ProviderOptions(CompilerSettingsHelper.CSC);
+            Assert.IsNotNull(opts);
+            Assert.AreEqual<string>(CompilerSettingsHelper.CSC.CompilerFullPath, opts.CompilerFullPath);   // Would include csc.exe or vbc.exe if the extension we searched for wasn't fake.
+            Assert.AreEqual<int>(CompilerSettingsHelper.CSC.CompilerServerTimeToLive, opts.CompilerServerTimeToLive);   // 10 in Production. 900 in a "dev" environment.
+            Assert.IsFalse(opts.UseAspNetSettings);  // Default via constructor is false.
+            Assert.IsFalse(opts.WarnAsError);
+            Assert.IsNull(opts.CompilerVersion);
+            Assert.AreEqual<int>(0, opts.AllOptions.Count);
+        }
+
         // <providerOptions> override defaults
         [TestMethod]
         public void FromProviderOptions()

RoslynCodeProviderTest/VBCodeProviderTests.cs

@@ -18,8 +18,10 @@ public class VBCodeProviderTests {
         private const int Failed = 1;
         private const int Success = 0;
 
+#pragma warning disable CS0618
         private CommonCodeDomProviderTests commonTests = new CommonCodeDomProviderTests();
         private CodeDomProvider _codeProvider = new VBCodeProvider(CompilerSettingsHelper.VB);
+#pragma warning restore CS0618
 
         [ClassInitialize]
         public static void ClassInitialize(TestContext context) {

src/Microsoft.CodeDom.Providers.DotNetCompilerPlatform/Util/ProviderOptions.cs

@@ -22,7 +22,11 @@ public ProviderOptions()
             this.CompilerFullPath = null;
             this.CompilerVersion = null;
             this.WarnAsError = false;
-            this.AllOptions = null;
+
+            // To be consistent, make sure there is always a dictionary here. It is less than ideal
+            // for some parts of code to be checking AllOptions.count and some part checking
+            // for AllOptions == null.
+            this.AllOptions = new ReadOnlyDictionary<string, string>(new Dictionary<string, string>());
 
             // This results in no keep-alive for the compiler. This will likely result in
             // slower performance for any program that calls out the the compiler any
@@ -48,7 +52,7 @@ public ProviderOptions(IProviderOptions opts)
             this.CompilerVersion = opts.CompilerVersion;
             this.WarnAsError = opts.WarnAsError;
             this.UseAspNetSettings = opts.UseAspNetSettings;
-            this.AllOptions = opts.AllOptions;
+            this.AllOptions = new ReadOnlyDictionary<string, string>(opts.AllOptions);
         }
 
         /// <summary>