Ensure that all subpackages are located correctly

src/NUnitEngine/nunit.engine/Internal/TestPackageExtensions.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+
+namespace NUnit.Engine.Internal
+{
+    public delegate bool TestPackageSelectorDelegate(TestPackage p);
+
+    /// <summary>
+    /// Extension methods for use with TestPackages
+    /// </summary>
+    public static class TestPackageExtensions
+    {
+        public static bool IsAssemblyPackage(this TestPackage package)
+        {
+            return package.FullName != null && PathUtils.IsAssemblyFileType(package.FullName);
+        }
+
+        public static bool HasSubPackages(this TestPackage package)
+        {
+            return package.SubPackages.Count > 0;
+        }
+
+        public static IList<TestPackage> Select(this TestPackage package, TestPackageSelectorDelegate selector)
+        {
+            var selection = new List<TestPackage>();
+
+            AccumulatePackages(package, selection, selector);
+
+            return selection;
+        }
+
+        private static void AccumulatePackages(TestPackage package, IList<TestPackage> selection, TestPackageSelectorDelegate selector)
+        {
+            if (selector(package))
+                selection.Add(package);
+
+            foreach (var subPackage in package.SubPackages)
+                AccumulatePackages(subPackage, selection, selector);
+        }
+    }
+}

src/NUnitEngine/nunit.engine/Runners/AggregatingTestRunner.cs

@@ -101,10 +101,6 @@ protected override TestEngineResult LoadPackage()
         {
             var results = new List<TestEngineResult>();
 
-            var packages = new List<TestPackage>(TestPackage.SubPackages);
-            if (packages.Count == 0)
-                packages.Add(TestPackage);
-
             foreach (var runner in Runners)
                 results.Add(runner.Load());
 

src/NUnitEngine/nunit.engine/Runners/DirectTestRunner.cs

@@ -99,15 +99,15 @@ protected override TestEngineResult LoadPackage()
         {
             var result = new TestEngineResult();
 
-            // DirectRunner may be called with a single-assembly package
-            // or a set of assemblies as subpackages.
-            var packages = TestPackage.SubPackages;
-            if (packages.Count == 0)
-                packages.Add(TestPackage);
+            // DirectRunner may be called with a single-assembly package,
+            // a set of assemblies as subpackages or even an arbitrary
+            // hierarchy of packages and subpackages with assemblies
+            // found in the terminal nodes.
+            var packagesToLoad = TestPackage.Select(p => !p.HasSubPackages());
 
             var driverService = Services.GetService<IDriverService>();
 
-            foreach (var subPackage in packages)
+            foreach (var subPackage in packagesToLoad)
             {
                 var testFile = subPackage.FullName;
 
@@ -207,12 +207,7 @@ protected override TestEngineResult RunTests(ITestEventListener listener, TestFi
 #if !NETSTANDARD1_6
             if (_assemblyResolver != null)
             {
-                var packages = TestPackage.SubPackages;
-
-                if (packages.Count == 0)
-                    packages.Add(TestPackage);
-
-                foreach (var package in packages)
+                foreach (var package in TestPackage.Select(p => p.IsAssemblyPackage()))
                     _assemblyResolver.RemovePathFromFile(package.FullName);
             }
 #endif