test: record how the emulator evaluates the queries the translator needs

tests/Cosmos.Tests.Infrastructure/Emulator.fs

@@ -203,6 +203,31 @@ let private isReachableAsync (cancellationToken : CancellationToken) : Task<bool
     | :? TaskCanceledException when not cancellationToken.IsCancellationRequested -> return false
 }
 
+/// <summary>
+/// The emulator that answers at <see cref="endpoint"/>.
+/// </summary>
+[<RequireQualifiedAccess>]
+type Kind =
+    /// The Windows emulator.
+    | Windows
+    /// The Linux vNext preview emulator, which CI and the dev container run.
+    | VNext
+
+/// <summary>
+/// Tells which <see cref="Kind"/> of emulator answers at <see cref="endpoint"/>, for the few query semantics in which
+/// the two differ: the Windows emulator answers an unauthenticated request to its root with HTTP 401, the vNext
+/// emulator with a success status.
+/// </summary>
+let readKindAsync (cancellationToken : CancellationToken) : Task<Kind> = task {
+    use httpClient = new HttpClient (createHttpMessageHandler (), true, Timeout = reachabilityTimeout)
+    use! response = httpClient.GetAsync (endpoint, cancellationToken)
+    return
+        if response.IsSuccessStatusCode then
+            Kind.VNext
+        else
+            Kind.Windows
+}
+
 /// <summary>
 /// Deletes the databases whose identifier starts with <see cref="DatabaseIdentifier.Prefix"/> and that stayed
 /// unmodified for at least the leftover age (<see cref="readLeftoverAge"/>): databases of tests whose cleanup failed

tests/Cosmos.Tests/FSharp.Azure.Cosmos.Tests.fsproj

@@ -38,6 +38,7 @@
     <Compile Include="ReadManyOperationTests.fs" />
     <Compile Include="ReadExtensionsTests.fs" />
     <Compile Include="IterationExtensionsTests.fs" />
+    <Compile Include="QuerySemanticsTests.fs" />
     <Compile Include="BuilderUnitTests.fs" />
   </ItemGroup>