feat: restructure docs into "chapters" (#12)

* feat(docker, k8s): create containers folder and kubernetes notes

docs/languages/dotnet/csharp/unit-tests.md

@@ -0,0 +1,51 @@
+# Unit Testing
+
+[UnitTest Overloaded Methods](https://stackoverflow.com/a/5666591/8319610)
+[Naming standards for unit tests](https://osherove.com/blog/2005/4/3/naming-standards-for-unit-tests.html)
+
+## xUnit
+
+```cs
+using System;
+using Xunit;
+
+namespace Project.Tests
+{
+    public class ClassTest
+    {
+        [Fact]
+        public void TestMethod()
+        {
+            Assert.Equal(expected, actual);  // works on collections
+            Assert.True(bool);
+            Assert.False(bool);
+            Assert.NotNull(nullable);
+
+            // Verifies that all items in the collection pass when executed against action
+            Assert.All<T>(IEnumerable<T> collection, Action<T> action);
+        }
+    }
+}
+```
+
+### Test Setup & Teardown
+
+xUnit.net creates a new instance of the test class for every test that is run, so any code which is placed into the constructor of the test class will be run for every single test.  
+This makes the constructor a convenient place to put reusable context setup code.
+
+For context cleanup, add the `IDisposable` interface to the test class, and put the cleanup code in the `Dispose()` method.
+
+## Mocking with Moq
+
+```cs
+var mockObj = new Mock<MockedType>();
+
+mockObj.Setup(m => m.Method(It.IsAny<InputType>())).Returns(value);
+mockObj.Object;  // get mock
+
+// check that the invocation is forwarded to the mock, n times
+mockObj.Verify(m => m.Method(It.IsAny<InputType>()), Times.Once());
+
+// check that the invocation is forwarded to the mock with a specific input
+mockObj.Verify(m => m.Method(input), Times.Once());
+```