├── .gitignore ├── LICENSE ├── README.md ├── TestPatterns.sln ├── src └── SystemUnderTest │ ├── Order.cs │ ├── OrderItem.cs │ ├── OrderService.cs │ ├── SystemUnderTest.csproj │ └── Utils.cs └── tests └── UnitTests ├── 01_PublicStateBased ├── OrderAddItem.cs └── OrderServicePlaceOrder.cs └── UnitTests.csproj /.gitignore: -------------------------------------------------------------------------------- 1 | ## Ignore Visual Studio temporary files, build results, and 2 | ## files generated by popular Visual Studio add-ons. 3 | ## 4 | ## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore 5 | 6 | # User-specific files 7 | *.rsuser 8 | *.suo 9 | *.user 10 | *.userosscache 11 | *.sln.docstates 12 | 13 | # User-specific files (MonoDevelop/Xamarin Studio) 14 | *.userprefs 15 | 16 | # Mono auto generated files 17 | mono_crash.* 18 | 19 | # Build results 20 | [Dd]ebug/ 21 | [Dd]ebugPublic/ 22 | [Rr]elease/ 23 | [Rr]eleases/ 24 | x64/ 25 | x86/ 26 | [Aa][Rr][Mm]/ 27 | [Aa][Rr][Mm]64/ 28 | bld/ 29 | [Bb]in/ 30 | [Oo]bj/ 31 | [Ll]og/ 32 | [Ll]ogs/ 33 | 34 | # Visual Studio 2015/2017 cache/options directory 35 | .vs/ 36 | # Uncomment if you have tasks that create the project's static files in wwwroot 37 | #wwwroot/ 38 | 39 | # Visual Studio 2017 auto generated files 40 | Generated\ Files/ 41 | 42 | # MSTest test Results 43 | [Tt]est[Rr]esult*/ 44 | [Bb]uild[Ll]og.* 45 | 46 | # NUnit 47 | *.VisualState.xml 48 | TestResult.xml 49 | nunit-*.xml 50 | 51 | # Build Results of an ATL Project 52 | [Dd]ebugPS/ 53 | [Rr]eleasePS/ 54 | dlldata.c 55 | 56 | # Benchmark Results 57 | BenchmarkDotNet.Artifacts/ 58 | 59 | # .NET Core 60 | project.lock.json 61 | project.fragment.lock.json 62 | artifacts/ 63 | 64 | # StyleCop 65 | StyleCopReport.xml 66 | 67 | # Files built by Visual Studio 68 | *_i.c 69 | *_p.c 70 | *_h.h 71 | *.ilk 72 | *.meta 73 | *.obj 74 | *.iobj 75 | *.pch 76 | *.pdb 77 | *.ipdb 78 | *.pgc 79 | *.pgd 80 | *.rsp 81 | *.sbr 82 | *.tlb 83 | *.tli 84 | *.tlh 85 | *.tmp 86 | *.tmp_proj 87 | *_wpftmp.csproj 88 | *.log 89 | *.vspscc 90 | *.vssscc 91 | .builds 92 | *.pidb 93 | *.svclog 94 | *.scc 95 | 96 | # Chutzpah Test files 97 | _Chutzpah* 98 | 99 | # Visual C++ cache files 100 | ipch/ 101 | *.aps 102 | *.ncb 103 | *.opendb 104 | *.opensdf 105 | *.sdf 106 | *.cachefile 107 | *.VC.db 108 | *.VC.VC.opendb 109 | 110 | # Visual Studio profiler 111 | *.psess 112 | *.vsp 113 | *.vspx 114 | *.sap 115 | 116 | # Visual Studio Trace Files 117 | *.e2e 118 | 119 | # TFS 2012 Local Workspace 120 | $tf/ 121 | 122 | # Guidance Automation Toolkit 123 | *.gpState 124 | 125 | # ReSharper is a .NET coding add-in 126 | _ReSharper*/ 127 | *.[Rr]e[Ss]harper 128 | *.DotSettings.user 129 | 130 | # TeamCity is a build add-in 131 | _TeamCity* 132 | 133 | # DotCover is a Code Coverage Tool 134 | *.dotCover 135 | 136 | # AxoCover is a Code Coverage Tool 137 | .axoCover/* 138 | !.axoCover/settings.json 139 | 140 | # Visual Studio code coverage results 141 | *.coverage 142 | *.coveragexml 143 | 144 | # NCrunch 145 | _NCrunch_* 146 | .*crunch*.local.xml 147 | nCrunchTemp_* 148 | 149 | # MightyMoose 150 | *.mm.* 151 | AutoTest.Net/ 152 | 153 | # Web workbench (sass) 154 | .sass-cache/ 155 | 156 | # Installshield output folder 157 | [Ee]xpress/ 158 | 159 | # DocProject is a documentation generator add-in 160 | DocProject/buildhelp/ 161 | DocProject/Help/*.HxT 162 | DocProject/Help/*.HxC 163 | DocProject/Help/*.hhc 164 | DocProject/Help/*.hhk 165 | DocProject/Help/*.hhp 166 | DocProject/Help/Html2 167 | DocProject/Help/html 168 | 169 | # Click-Once directory 170 | publish/ 171 | 172 | # Publish Web Output 173 | *.[Pp]ublish.xml 174 | *.azurePubxml 175 | # Note: Comment the next line if you want to checkin your web deploy settings, 176 | # but database connection strings (with potential passwords) will be unencrypted 177 | *.pubxml 178 | *.publishproj 179 | 180 | # Microsoft Azure Web App publish settings. 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IN NO EVENT SHALL THE 18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 21 | SOFTWARE. 22 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Test Patterns 2 | 3 | Examples of approaches to unit testing different kinds of code in C#. These examples start with simple cases and move on to more complex patterns. 4 | 5 | ## Give a Star! :star: 6 | 7 | If you like or are using this project to learn, please give it a star to help others find it. Thanks! 8 | 9 | ## State-Based Testing 10 | 11 | The simplest kinds of unit tests create collaborators, call methods, and inspect the results. These work best with public methods with non-void return signatures and no side effects. 12 | 13 | ### Resources and Practice 14 | 15 | Tests should follow [SOLID principles](https://www.pluralsight.com/courses/csharp-solid-principles), including Single Responsibility. Grouping tests by the method being tested helps achieve this. Read the following naming convention for a proven approach to organizing and naming your tests. Also, the FizzBuzz and String Calculator katas are great to use when first learning state-based testing. 16 | 17 | - [Test Naming Convention](https://ardalis.com/unit-test-naming-convention) 18 | - [FizzBuzz Kata](https://github.com/ardalis/kata-catalog/blob/master/katas/FizzBuzz.md) 19 | - [String Calculator Kata](https://github.com/ardalis/kata-catalog/blob/master/katas/String%20Calculator.md) 20 | 21 | ## Behavior-Based Testing (with Mocks) 22 | 23 | When you can't evaluate whether a method did the right thing by looking at the state it returns or modifies publicly, another approach is to test the behavior of the method itself. This is often called "behavior-based" testing and frequently uses *mock objects* (or spies or fakes or other techniques) to capture behavior that took place within the method being tested. Collectively these different techniques are known as [test doubles](http://xunitpatterns.com/Test%20Double.html). 24 | 25 | ### Resources and Practice 26 | 27 | - [Test Doubles](http://xunitpatterns.com/Test%20Double.html) 28 | - [File Logger Kata](https://github.com/ardalis/kata-catalog/blob/master/katas/File%20Logger.md) 29 | 30 | ## Testing Hard-To-Access State 31 | 32 | Confirming the state of private or internal values when testing from another class and assembly can be a challenge. There are some patterns that can be used to overcome these challenges in most cases. 33 | 34 | 35 | 36 | -------------------------------------------------------------------------------- /TestPatterns.sln: -------------------------------------------------------------------------------- 1 |  2 | Microsoft Visual Studio Solution File, Format Version 12.00 3 | # Visual Studio Version 16 4 | VisualStudioVersion = 16.0.29609.76 5 | MinimumVisualStudioVersion = 10.0.40219.1 6 | Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{789B035D-5356-4AA3-9409-DE85385D712E}" 7 | EndProject 8 | Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "tests", "tests", "{B38B0496-E490-48BF-8B15-88082FFD1E67}" 9 | EndProject 10 | Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "SystemUnderTest", "src\SystemUnderTest\SystemUnderTest.csproj", "{ABEF74F3-24AB-4BB2-9383-EBC1A72D65F5}" 11 | EndProject 12 | Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "UnitTests", "tests\UnitTests\UnitTests.csproj", "{90192EFD-5BA8-4E1B-B2BB-FF9BAA4A32C8}" 13 | EndProject 14 | Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{34676D38-5239-4A27-B9DE-D7E0E7997D04}" 15 | ProjectSection(SolutionItems) = preProject 16 | README.md = README.md 17 | EndProjectSection 18 | EndProject 19 | Global 20 | GlobalSection(SolutionConfigurationPlatforms) = preSolution 21 | Debug|Any CPU = Debug|Any CPU 22 | Release|Any CPU = Release|Any CPU 23 | EndGlobalSection 24 | GlobalSection(ProjectConfigurationPlatforms) = postSolution 25 | {ABEF74F3-24AB-4BB2-9383-EBC1A72D65F5}.Debug|Any CPU.ActiveCfg = Debug|Any CPU 26 | {ABEF74F3-24AB-4BB2-9383-EBC1A72D65F5}.Debug|Any CPU.Build.0 = Debug|Any CPU 27 | {ABEF74F3-24AB-4BB2-9383-EBC1A72D65F5}.Release|Any CPU.ActiveCfg = Release|Any CPU 28 | {ABEF74F3-24AB-4BB2-9383-EBC1A72D65F5}.Release|Any CPU.Build.0 = Release|Any CPU 29 | {90192EFD-5BA8-4E1B-B2BB-FF9BAA4A32C8}.Debug|Any CPU.ActiveCfg = Debug|Any CPU 30 | {90192EFD-5BA8-4E1B-B2BB-FF9BAA4A32C8}.Debug|Any CPU.Build.0 = Debug|Any CPU 31 | {90192EFD-5BA8-4E1B-B2BB-FF9BAA4A32C8}.Release|Any CPU.ActiveCfg = Release|Any CPU 32 | {90192EFD-5BA8-4E1B-B2BB-FF9BAA4A32C8}.Release|Any CPU.Build.0 = Release|Any CPU 33 | EndGlobalSection 34 | GlobalSection(SolutionProperties) = preSolution 35 | HideSolutionNode = FALSE 36 | EndGlobalSection 37 | GlobalSection(NestedProjects) = preSolution 38 | {ABEF74F3-24AB-4BB2-9383-EBC1A72D65F5} = {789B035D-5356-4AA3-9409-DE85385D712E} 39 | {90192EFD-5BA8-4E1B-B2BB-FF9BAA4A32C8} = {B38B0496-E490-48BF-8B15-88082FFD1E67} 40 | EndGlobalSection 41 | GlobalSection(ExtensibilityGlobals) = postSolution 42 | SolutionGuid = {8C69494F-5684-47A6-ACB2-DA70FF5720B4} 43 | EndGlobalSection 44 | EndGlobal 45 | -------------------------------------------------------------------------------- /src/SystemUnderTest/Order.cs: -------------------------------------------------------------------------------- 1 | using System.Collections.Generic; 2 | 3 | namespace SystemUnderTest 4 | { 5 | public class Order 6 | { 7 | public string CustomerEmail { get; } 8 | private List _items = new List(); 9 | public IEnumerable Items => _items.AsReadOnly(); 10 | 11 | // An easily tested public method with return type and modified public property 12 | public bool AddItem(OrderItem item) 13 | { 14 | if (item == null) return false; 15 | _items.Add(item); 16 | return true; 17 | } 18 | } 19 | } 20 | -------------------------------------------------------------------------------- /src/SystemUnderTest/OrderItem.cs: -------------------------------------------------------------------------------- 1 | namespace SystemUnderTest 2 | { 3 | public class OrderItem 4 | { } 5 | } 6 | -------------------------------------------------------------------------------- /src/SystemUnderTest/OrderService.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Linq; 3 | 4 | namespace SystemUnderTest 5 | { 6 | public class OrderService 7 | { 8 | private int _orderCount = 0; 9 | 10 | // A void method whose success cannot be verified by its returned result 11 | // Verifying thrown exceptions is straightforward, but what about successful execution? 12 | public void PlaceOrder(Order order) 13 | { 14 | if (order == null) throw new ArgumentNullException(nameof(order)); 15 | 16 | if(!order.Items.Any()) 17 | { 18 | return; 19 | } 20 | 21 | SaveOrder(order); 22 | 23 | Utils.SendOrderConfirmationEmail(order); 24 | 25 | _orderCount++; 26 | } 27 | 28 | private void SaveOrder(Order order) 29 | { 30 | throw new Exception("Can't connect to database."); 31 | } 32 | } 33 | } 34 | -------------------------------------------------------------------------------- /src/SystemUnderTest/SystemUnderTest.csproj: -------------------------------------------------------------------------------- 1 | 2 | 3 | 4 | netstandard2.0 5 | 6 | 7 | 8 | -------------------------------------------------------------------------------- /src/SystemUnderTest/Utils.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | 3 | namespace SystemUnderTest 4 | { 5 | public class Utils 6 | { 7 | public static void SendOrderConfirmationEmail(Order order) 8 | { 9 | throw new Exception("Cannot connect to email server."); 10 | } 11 | 12 | public static void SaveOrder(Order order) 13 | { 14 | // save the order somewhere 15 | } 16 | } 17 | } 18 | -------------------------------------------------------------------------------- /tests/UnitTests/01_PublicStateBased/OrderAddItem.cs: -------------------------------------------------------------------------------- 1 | using SystemUnderTest; 2 | using Xunit; 3 | 4 | namespace UnitTests 5 | { 6 | 7 | /// 8 | /// These tests call a public method and verify its result is what is expected 9 | /// They also confirm a side effect in a public property 10 | /// 11 | public class OrderAddItem 12 | { 13 | private Order _order = new Order(); 14 | 15 | [Fact] 16 | public void ReturnsFalseGivenNullItem() 17 | { 18 | var result = _order.AddItem(null); 19 | 20 | Assert.False(result); 21 | } 22 | 23 | [Fact] 24 | public void ReturnsTrueGivenNonNullItem() 25 | { 26 | var result = _order.AddItem(new OrderItem()); 27 | 28 | Assert.True(result); 29 | } 30 | 31 | [Fact] 32 | public void AddsItemToItemsCollection() 33 | { 34 | var item = new OrderItem(); 35 | _order.AddItem(item); 36 | 37 | Assert.Contains(item, _order.Items); 38 | } 39 | } 40 | } 41 | -------------------------------------------------------------------------------- /tests/UnitTests/01_PublicStateBased/OrderServicePlaceOrder.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using SystemUnderTest; 3 | using Xunit; 4 | 5 | namespace UnitTests 6 | { 7 | public class OrderServicePlaceOrder 8 | { 9 | private OrderService _orderService = new OrderService(); 10 | 11 | [Fact] 12 | public void ThrowsArgumentNullExceptionGivenNullOrder() 13 | { 14 | var exception = Assert.Throws(() => _orderService.PlaceOrder(null)); 15 | 16 | Assert.Equal("order", exception.ParamName); 17 | } 18 | 19 | [Fact] 20 | public void DoesNothingGivenEmptyOrder() 21 | { 22 | _orderService.PlaceOrder(new Order()); 23 | 24 | // nothing else to assert. If we get here without exception, we pass? 25 | } 26 | } 27 | } 28 | -------------------------------------------------------------------------------- /tests/UnitTests/UnitTests.csproj: -------------------------------------------------------------------------------- 1 |  2 | 3 | 4 | netcoreapp3.1 5 | 6 | false 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | --------------------------------------------------------------------------------