Rework tests from 1-to-1 mapping into specifications (#46)

CliFx.Tests/DependencyInjectionSpecs.cs

@@ -0,0 +1,58 @@
+using CliFx.Exceptions;
+using FluentAssertions;
+using Xunit;
+
+namespace CliFx.Tests
+{
+    public partial class DependencyInjectionSpecs
+    {
+        [Fact]
+        public void Default_type_activator_can_initialize_a_command_if_it_has_a_parameterless_constructor()
+        {
+            // Arrange
+            var activator = new DefaultTypeActivator();
+
+            // Act
+            var obj = activator.CreateInstance(typeof(WithoutDependenciesCommand));
+
+            // Assert
+            obj.Should().BeOfType<WithoutDependenciesCommand>();
+        }
+
+        [Fact]
+        public void Default_type_activator_cannot_initialize_a_command_if_it_does_not_have_a_parameterless_constructor()
+        {
+            // Arrange
+            var activator = new DefaultTypeActivator();
+
+            // Act & assert
+            Assert.Throws<CliFxException>(() =>
+                activator.CreateInstance(typeof(WithDependenciesCommand)));
+        }
+
+        [Fact]
+        public void Delegate_type_activator_can_initialize_a_command_using_a_custom_function()
+        {
+            // Arrange
+            var activator = new DelegateTypeActivator(_ =>
+                new WithDependenciesCommand(new DependencyA(), new DependencyB()));
+
+            // Act
+            var obj = activator.CreateInstance(typeof(WithDependenciesCommand));
+
+            // Assert
+            obj.Should().BeOfType<WithDependenciesCommand>();
+        }
+
+        [Fact]
+        public void Delegate_type_activator_throws_if_the_underlying_function_returns_null()
+        {
+            // Arrange
+            var activator = new DelegateTypeActivator(_ => null);
+
+            // Act & assert
+            Assert.Throws<CliFxException>(() =>
+                activator.CreateInstance(typeof(WithDependenciesCommand)));
+        }
+    }
+}