Add test CanGetPSReadLineProxy

Which asserts that we can successfully load PSReadLine.

Author: andyleejordan

src/PowerShellEditorServices/Services/PowerShellContext/Session/PSReadLinePromptContext.cs

@@ -22,6 +22,13 @@ internal class PSReadLinePromptContext : IPromptContext
             "..",
             "..",
             "..",
+#if TEST
+            // When using xUnit (dotnet test) the assemblies are deployed to the
+            // test project folder, invalidating our relative path assumption.
+            "..",
+            "..",
+            "module",
+#endif
             "PSReadLine");
 
         private static readonly Lazy<CmdletInfo> s_lazyInvokeReadLineForEditorServicesCmdletInfo = new Lazy<CmdletInfo>(() =>

test/PowerShellEditorServices.Test/Session/PowerShellContextTests.cs

@@ -143,6 +143,16 @@ await this.powerShellContext.ExecuteCommandAsync<string>(
             Assert.Equal(expectedString, result.FirstOrDefault(), true);
         }
 
+        [Trait("Category", "PSReadLine")]
+        [Fact]
+        public async Task CanGetPSReadLineProxy()
+        {
+            Assert.True(PSReadLinePromptContext.TryGetPSReadLineProxy(
+                NullLogger.Instance,
+                PowerShellContextFactory.initialRunspace,
+                out PSReadLineProxy proxy));
+        }
+
         #region Helper Methods
 
         private async Task AssertStateChange(PowerShellContextState expectedState)