Add tests to test-project

test-project/Assets/Tests/PlayMode/PlayModeTests.asmdef

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+{
+    "name": "PlayModeTests",
+    "references": [
+        "UnityEngine.TestRunner",
+        "UnityEditor.TestRunner"
+    ],
+    "includePlatforms": [],
+    "excludePlatforms": [],
+    "allowUnsafeCode": false,
+    "overrideReferences": true,
+    "precompiledReferences": [
+        "nunit.framework.dll"
+    ],
+    "autoReferenced": false,
+    "defineConstraints": [
+        "UNITY_INCLUDE_TESTS"
+    ],
+    "versionDefines": []
+}

test-project/Assets/Tests/PlayMode/PlayModeTests.asmdef.meta

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+guid: d391d6383db8bd145a52b5d66c74e13e
+AssemblyDefinitionImporter:
+  externalObjects: {}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 

test-project/Assets/Tests/PlayMode/SamplePlayModeTest.cs

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+using System.Collections;
+using System.Collections.Generic;
+using NUnit.Framework;
+using UnityEngine;
+using UnityEngine.TestTools;
+
+namespace Tests
+{
+  public class SamplePlayModeTest
+  {
+    // A Test behaves as an ordinary method
+    [Test]
+    public void NewTestScriptSimplePasses()
+    {
+      // Use the Assert class to test conditions
+      Assert.True(true);
+    }
+
+    // A UnityTest behaves like a coroutine in Play Mode. In Edit Mode you can use
+    // `yield return null;` to skip a frame.
+    [UnityTest]
+    public IEnumerator NewTestScriptWithEnumeratorPasses()
+    {
+      // Use the Assert class to test conditions.
+      // Use yield to skip a frame.
+      yield return null;
+    }
+  }
+}

test-project/Assets/Tests/PlayMode/SamplePlayModeTest.cs.meta

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+guid: d385608e408f6ae4c94f785127ed731c
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData:
+  assetBundleName:
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