Stryker.NET

https://github.com/stryker-mutator/stryker-net
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Stryker.NET is a mutation testing tool for .NET Core and .NET Framework projects that validates test...
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### Install and run Stryker.NET with dotnet tool

Source: https://github.com/stryker-mutator/stryker-net/blob/master/README.md

Use these commands to install the dotnet-stryker tool globally and run it in your test project folder. The first command installs the tool, the second navigates to the test project directory, and the third executes Stryker to perform mutation testing.

```bash
dotnet tool install -g dotnet-stryker
cd /my/unit/test/project/folder
dotnet stryker
```

--------------------------------

### stryker-config.yaml example

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Example YAML configuration file for Stryker. Place it in the unit test project folder and name it stryker-config.yaml. The configuration section must be called stryker-config.

```yaml
  stryker-config:
    solution: '../SolutionFile.sln'
    project: 'ExampleProject.csproj'
```

--------------------------------

### Create tool manifest

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/getting-started.md

Creates a dotnet-tools.json file in the project folder for local tool installation.

```bash
dotnet new tool-manifest
```

--------------------------------

### Install Stryker in Azure DevOps with --tool-path

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/stryker-in-pipeline.md

Uses DotNetCoreCLI@2 task to install dotnet-stryker as a local tool with --tool-path pointing to $(Agent.BuildDirectory)/tools.

```yaml
- task: DotNetCoreCLI@2
    displayName: 'Install dotnet-stryker'
    inputs:
      command: custom
      custom: tool
      arguments: install dotnet-stryker --tool-path $(Agent.BuildDirectory)/tools
```

--------------------------------

### Install Stryker globally

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/getting-started.md

Installs Stryker as a global dotnet tool using the -g flag.

```bash
dotnet tool install -g dotnet-stryker
```

--------------------------------

### Stryker configuration file

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/getting-started.md

Example stryker-config.json file to store options like reporters, so they don't need to be passed via CLI each run.

```json
{
    "stryker-config":
    {
        "reporters": [
            "progress",
            "html"
        ]
    }
}
```

--------------------------------

### Copy VS Code configuration templates

Source: https://github.com/stryker-mutator/stryker-net/blob/master/CONTRIBUTING.md

Copy the example VS Code configuration files to create local launch and tasks configurations. Use these commands on macOS/Linux; on Windows, manually copy the contents.

```bash
cp .vscode/launch.json.example .vscode/launch.json
cp .vscode/tasks.json.example .vscode/tasks.json
```

--------------------------------

### Install Stryker locally

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/getting-started.md

Installs Stryker as a local tool without the -g flag, after creating the tool manifest.

```bash
dotnet tool install dotnet-stryker
```

--------------------------------

### Stryker comments example in C#

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/ignore-mutations.md

Example showing how to use Stryker comments to control mutation testing at the source level. It demonstrates 'disable all', 'restore all', and 'disable once' with specific mutator lists.

```csharp
var i = 0;
var y = 10;
// Stryker disable all : for explanatory reasons
i++; // won't be mutated
y++; // won't be mutated
// Stryker restore all
i--; // will be mutated
i++; // will be mutated
// Stryker disable once Arithmetic
y++; // will be mutated
// Stryker disable once Arithmetic,Update
i--; // won't be mutated
```

--------------------------------

### Enable dashboard baseline in Azure DevOps with --with-baseline

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/stryker-in-pipeline.md

Starts baseline run comparing against the target branch and uses dashboard API key and source branch version.

```bash
dotnet stryker --with-baseline:$(System.PullRequest.TargetBranch) --dashboard-api-key $(Stryker.Dashboard.Api.Key) --version $(System.PullRequest.SourceBranch)
```

--------------------------------

### Baseline fallback-version resolution examples

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Shows the fallback-version resolution logic for the baseline feature. The first block is the configuration input; the following blocks are the possible outcomes depending on whether a baseline exists for the current branch and the fallback branch. When no baseline is found, a complete testrun is performed and saved as the new baseline.

```json
"since-target": 'development',
"current-branch" 'feat-2'
```

```json
baseline exists for branch feat-2: false
baseline exists for branch development: false

baseline used: null (complete instead of partial testrun)
new baseline saved to: feat-2
```

```json
baseline exists for branch feat-2: false
baseline exists for branch development: true

baseline used: development
new baseline saved to: feat-2
```

```json
baseline exists for branch feat-2: true
baseline exists for branch development: true

baseline used: feat-2
new baseline saved to: feat-2
```

--------------------------------

### Run locally installed dotnet-stryker in Azure DevOps

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/stryker-in-pipeline.md

Runs the tool installed in the common agent folder using a PowerShell inline script.

```yaml
- task: Powershell@2
    displayName: 'Run dotnet-stryker'
    inputs:
      workingDirectory: <test-project-folder-here>
      targetType: 'inline'
      pwsh: true
      script: $(Agent.BuildDirectory)/tools/dotnet-stryker
```

--------------------------------

### Mutant schemata if statement example

Source: https://github.com/stryker-mutator/stryker-net/wiki/2.-Research

Shows the mutant schemata technique where all mutations are placed inside if statements controlled by an environment variable. The mutated code is executed when the variable matches, otherwise the original code runs.

```csharp
if(Environment.GetEnvironmentVariable("ActiveMutation") == "1") {
  i--; // mutated code
} else {
  i++; // original code
}
```

--------------------------------

### NUnit test execution run sequence

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/technical-reference/testing-framework.md

Shows the sequence of events during NUnit test execution with TestCaseSource, including when the data source is enumerated and when test cases start and end.

```text
NUnit runner calls the TestCaseSource and gets every test case.
TestSession start event
 ...
   NUnit discovers test
     NUnit enumerates data source (for tests)
...
  
TestCase start event
   NUnit run test with first set of data
   NUnit run test with second set of data
   ...
   NUnit reports test result
TestCase end event
   ...
   NUnit reports last test result
TestCase end event
TestCase start event
   ...

```

--------------------------------

### Example of ignored method mutation in C#

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Shows that method calls with constant arguments (e.g., ConfigureAwait(true)) are skipped, while calls with variable arguments (e.g., ConfigureAwait(t)) are not detected and thus not skipped.

```csharp
// This mutation will be skipped
ConfigureAwait(true); 

// This mutation won't because we cannot currently detect this
var t = true;
ConfigureAwait(t); 
```

--------------------------------

### Statement and block removal mutations

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates statements and blocks by removing them. For example, `void Function() { Age++; }` becomes an empty block, `return;` is removed, and `MyMethodCall();` is removed.

```csharp
`void Function() { Age++; }`
```

```csharp
`void Function() {} (block emptied)`
```

```csharp
`int Function() { Age++; return Age; }`
```

```csharp
`void Function() { return default; } (block emptied)`
```

```csharp
`return;`
```

```csharp
`removed`
```

```csharp
`return value;`
```

```csharp
`break;`
```

```csharp
`continue;`
```

```csharp
`goto;`
```

```csharp
`throw;`
```

```csharp
`throw exception;`
```

```csharp
`yield return value;`
```

```csharp
`yield break;`
```

```csharp
`MyMethodCall();`
```

--------------------------------

### C# example of constant value mutation limitation

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/technical-reference/mutant-schemata.md

Shows an enum with a constant expression that cannot be mutated because MutantControl.IsActive(0) is not a constant value. Stryker.NET skips mutating constant values for this reason.

```cs
public enum Numbers
{
    One = 1,
    Two = (One + 1)
}
```

--------------------------------

### Stryker disable once within an expression

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/ignore-mutations.md

Use the 'once' keyword within an expression to ignore mutations only for the next syntax construct. In this example, only mutations impacting SomeMethod(x*5) are ignored.

```csharp
x = x + 
// Stryker disable once Arithmetic
SomeMethod(x*5)
* SomeOtherMethod(x/2);
```

--------------------------------

### C# example of attempted mutation of constant value

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/technical-reference/mutant-schemata.md

Shows the attempted mutation of the constant expression in the enum, which would not compile because MutantControl.IsActive(0) is not a constant value. This illustrates why constant values are skipped.

```cs
public enum Numbers
{
    One = 1,
    Two = (MutantControl.IsActive(0) ? (One - 1) : (One + 1))
}
```

--------------------------------

### Assignment operator mutations

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates compound assignment operators to their counterparts. For example, `+=` becomes `-=`, `*=` becomes `/=`, and `??=` becomes `=`. Note that `&=` and `|=` have two possible mutations each.

```csharp
`+=`
```

```csharp
`-=`
```

```csharp
`*=`
```

```csharp
`/=`
```

```csharp
`%=`
```

```csharp
`<<=`
```

```csharp
`>>=`
```

```csharp
`&=`
```

```csharp
`^=`
```

```csharp
`|=`
```

```csharp
`??=`
```

--------------------------------

### Constant value mutation example: enum

Source: https://github.com/stryker-mutator/stryker-net/wiki/3.-Mutant-schemata

Demonstrates a constant value that cannot be mutated because the generated code would not compile. The original enum uses a constant expression, but the mutated version uses a non-constant method call.

```cs
public enum Numbers
{
    One = 1,
    Two = (One + 1)
}
```

```cs
public enum Numbers
{
    One = 1,
    Two = (MutantControl.IsActive(0) ? (One - 1) : (One + 1))
}
```

--------------------------------

### Scope error example: variable declaration inside if

Source: https://github.com/stryker-mutator/stryker-net/wiki/3.-Mutant-schemata

Illustrates a mutation that changes variable scope, causing a compile error because 'i' is not accessible after the if statement. The error location is at the return statement, making rollback difficult.

```csharp
if (Environment.GetEnvironmentVariable("ActiveMutation") == "1") {
  int i = 0; // mutated code
} else {
  int i = 99; // original code
}
return i;
```

--------------------------------

### Initializer mutations

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates collection and object initializers by emptying their contents. For example, `new int[] { 1, 2 }` becomes `new int[] { }`, and `new SomeClass { Foo = "Bar" }` becomes `new SomeClass { }`.

```csharp
`new int[] { 1, 2 };`
```

```csharp
`new int[] { };`
```

```csharp
`int[] numbers = { 1, 2 };`
```

```csharp
`int[] numbers = { };`
```

```csharp
`new List<int> { 1, 2 };`
```

```csharp
`new List<int> { };`
```

```csharp
`new Collection<int> { 1, 2 };`
```

```csharp
`new Collection<int> { };`
```

```csharp
`new Dictionary<int, int> { { 1, 1 } };`
```

```csharp
`new Dictionary<int, int> { };`
```

```csharp
`new SomeClass { Foo = "Bar" };`
```

```csharp
`new SomeClass { };`
```

--------------------------------

### Compile error example: string subtraction mutation

Source: https://github.com/stryker-mutator/stryker-net/wiki/3.-Mutant-schemata

Shows a mutation that causes a compile error because subtracting strings is invalid. The mutated code is inside an if statement checking the 'ActiveMutation' environment variable, while the original code is in the else branch.

```csharp
if (Environment.GetEnvironmentVariable("ActiveMutation") == "1") {
  return "hello " - "world"; // mutated code
} else {
  return "hello " + "world"; // original code
}
```

--------------------------------

### Initialize Stryker with custom config file name

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Creates a configuration file with a custom name.

```bash
dotnet stryker init --config-file "custom.json"
```

--------------------------------

### Initialize Stryker configuration

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Initializes a new JSON configuration file in the current directory.

```bash
dotnet stryker init
```

--------------------------------

### Run Stryker with --project option

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/operating-modes.md

Specify the source project with --project when the test project has multiple project references. Only one source project can be specified at a time.

```bash
cd /my-solution-dir/my-test-project-dir
dotnet stryker --project <filename>
```

--------------------------------

### Run Stryker from source project with --test-project

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/operating-modes.md

Run Stryker from the source project context, passing the test project location with --test-project.

```bash
cd /my-solution-dir/my-source-project-dir
dotnet stryker --test-project "../my-test-project-dir/tests.csproj"
```

--------------------------------

### Run Stryker.NET with markdown reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Run Stryker.NET with the markdown reporter to generate a Markdown summary file named mutation-report.md in the StrykerOutput/{date-time}/reports directory.

```bash
dotnet stryker --reporter "markdown"
```

--------------------------------

### Enable HTML reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Activates the HTML reporter, which outputs an HTML file visually displaying the project and all mutations. Recommended for larger projects.

```bash
dotnet stryker --reporter "html"
```

--------------------------------

### Run Stryker

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/getting-started.md

Runs Stryker with default configuration, which will find the source project to mutate.

```bash
dotnet stryker
```

--------------------------------

### Run Stryker with explicit solution file

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/operating-modes.md

Pass a specific solution file using the --solution option. Stryker prioritizes the solution context over the project context if both solution and project files are in the same folder.

```bash
cd /my-solution-dir
dotnet stryker --solution "/my-solution-dir/mysolution.sln"
```

--------------------------------

### Run Stryker from solution directory

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/operating-modes.md

Run Stryker from the solution directory. Stryker discovers a single solution file and mutates all projects it can find.

```bash
cd /my-solution-dir
dotnet stryker
```

--------------------------------

### Run Stryker with multiple --test-project options

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/operating-modes.md

Specify multiple test projects targeting the same source project by repeating the --test-project option.

```bash
cd /my-solution-dir/my-source-project-dir
dotnet stryker --test-project "../my-test-project-dir/Tests.csproj" --test-project "../my-test-project-dir/MoreTests.csproj"
```

--------------------------------

### Run Stryker with dots reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Use this reporter on build servers for little/no performance loss while still giving insight. It indicates in a very simple way how many mutants have been tested and their status: "." means killed, "S" means survived, and "T" means timed out.

```bash
dotnet stryker --reporter "dots"
```

--------------------------------

### Run Stryker with cleartext reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Use this reporter for a quick run without leaving files on your system. It displays all files right after the mutation testrun is done.

```bash
dotnet stryker --reporter "cleartext"
```

--------------------------------

### New multi-value reporter option (V1.x)

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/migration-guide.md

Shows the new, standard way to pass multiple reporters by repeating the --reporter flag. This replaces the old array syntax.

```shell
dotnet stryker --reporter "html" --reporter "progress"
```

--------------------------------

### Enable SourceLink with DotNet.ReproducibleBuilds

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Adds the DotNet.ReproducibleBuilds package to a .csproj or Directory.Build.props file to enable SourceLink, which allows Stryker to automatically retrieve the project name and version for the dashboard reporter.

```xml
  <ItemGroup>
    <PackageReference Include="DotNet.ReproducibleBuilds" Version="0.1.66" PrivateAssets="All"/>
  </ItemGroup>
```

--------------------------------

### Initialize Stryker with CLI option override

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Overrides default values using regular CLI options.

```bash
dotnet stryker init --mutation-level "advanced"
```

--------------------------------

### Run Stryker with cleartexttree reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Use this reporter for a quick run without leaving files on your system. It displays all mutations right after the mutation testrun is done. It is recommended to turn this reporter off on big projects.

```bash
dotnet stryker --reporter "cleartexttree"
```

--------------------------------

### Run Stryker from test project directory

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/operating-modes.md

Run Stryker from the test project folder. Stryker automatically detects the source project based on the project reference.

```bash
cd /my-solution-dir/my-test-project-dir
dotnet stryker
```

--------------------------------

### Check dotnet version

Source: https://github.com/stryker-mutator/stryker-net/blob/master/CONTRIBUTING.md

Verify that the dotnet CLI is available and in your PATH. This helps troubleshoot 'Command not found' errors when running VS Code tasks.

```bash
dotnet --version
```

--------------------------------

### Run Stryker with trace logging

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/getting-started.md

Runs Stryker with trace logging enabled to troubleshoot issues, writing logs to a file.

```bash
dotnet stryker --verbosity trace --log-to-file
```

--------------------------------

### Enable progress reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Activates the progress reporter, which outputs the current status of the mutation test run with a visual progress bar and estimated completion time. Recommended for large projects.

```bash
dotnet stryker --reporter "progress"
```

--------------------------------

### Run Stryker with json reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Use this reporter to output a json file with all mutation testrun info of the last run. The json is also used for the HTML reporter, but using this reporter you could use the file for your own purposes.

```bash
dotnet stryker --reporter "json"
```

--------------------------------

### Run Stryker with gitlab reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Use this reporter to output a json file named `gitlab_quality.json` with all mutation testrun info of the last run. The json structure follows the GitLab Code Quality report format defined in GitLab Docs.

```bash
dotnet stryker --reporter "gitlab"
```

--------------------------------

### Old multi-value reporters option (V0.x)

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/migration-guide.md

Shows the old, non-standard way to pass multiple reporters via a single CLI flag, using a JSON-like array string. This is deprecated in V1.x.

```shell
dotnet stryker --reporters "['html', 'progress']"
```

--------------------------------

### Run Stryker with debug verbosity

Source: https://github.com/stryker-mutator/stryker-net/blob/master/CONTRIBUTING.md

Run Stryker with debug verbosity to capture detailed output for bug reports. Add the output to the issue.

```bash
dotnet stryker --verbosity debug
```

--------------------------------

### Enable dashboard reporter

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/reporters.md

Activates the dashboard reporter, which uploads Stryker results as JSON to the Stryker dashboard. Requires configuration of API key, project name, and project version (unless using SourceLink).

```bash
dotnet stryker --reporter "dashboard"
```

--------------------------------

### JavaScript to set report and theme

Source: https://github.com/stryker-mutator/stryker-net/blob/master/src/Stryker.Core/Stryker.Core/Reporters/Html/Files/mutation-report.html

This script sets the report data on the app element and updates the theme background color. It listens for theme changes and applies the background color to the body.

```javascript
const app = document.querySelector('mutation-test-report-app');
app.report = ##REPORT_JSON##;
function updateTheme() {
  document.body.style.backgroundColor = app.themeBackgroundColor;
}
app.addEventListener('theme-changed', updateTheme);
updateTheme();
```

--------------------------------

### Stryker config with Dashboard baseline provider

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/stryker-in-pipeline.md

Minimal JSON configuration for setting the baseline provider to Dashboard.

```json
{
  "stryker-config": {
    "baseline": {
      "provider": "Dashboard"
    }
  }
}
```

--------------------------------

### Set mutation score break threshold with --break-at

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/stryker-in-pipeline.md

Configure a break threshold to fail the pipeline when the mutation score falls below 80.

```bash
dotnet stryker --break-at 80
```

--------------------------------

### xUnit test execution timeline

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/technical-reference/testing-framework.md

Timeline of xUnit test execution in Stryker.NET. Shows discovery, theory enumeration, and per-test-case execution with multiple data sets. Note that each test result includes the total execution time for all data sets, so results should not be summed.

```text
TestSession start event
xUnit discovers test
   xUnit discovers theories
     xUnit enumerates data source (for tests)
...
TestCase start event
   xUnit runs test with first set of data
   xUnit runs test with second set of data
   ...
   xUnit runs test with last set of data

   xUnit reports first test results
TestCase end event
   xUnit reports second test result
   ...
   xUnit reports last test result
TestCase start event
   ...
TestSession end event
```

--------------------------------

### Restore local tools

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/getting-started.md

Restores or updates the local Stryker tool for the team using the dotnet-tools.json file.

```bash
dotnet tool restore
```

--------------------------------

### Publish mutation report with PublishMutationReport@1

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/stryker-in-pipeline.md

Adds the mutation report to the build summary in Azure DevOps pipelines.

```yaml
- task: PublishMutationReport@1
  displayName: 'Publish Mutation Test Report'
  inputs:
    reportPattern: '**/mutation-report.html'
```

--------------------------------

### Mutate option to ignore files

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/ignore-mutations.md

Ignore whole files from mutation testing using the mutate option with a glob pattern. The JSON configuration and the equivalent command-line flag -m are shown.

```json
"stryker-config": {
    "mutate": ["!**/*.Generated.cs"]
}
```

```bash
-m "!**/*.Generated.cs"
```

--------------------------------

### HTML custom element placeholder

Source: https://github.com/stryker-mutator/stryker-net/blob/master/src/Stryker.Core/Stryker.Core/Reporters/Html/Files/mutation-report.html

The page includes a custom element 'mutation-test-report-app' where the report is rendered. The browser must support custom elements for the report to display.

```html
<mutation-test-report-app></mutation-test-report-app>
```

--------------------------------

### Conditional statement solution for scope errors

Source: https://github.com/stryker-mutator/stryker-net/wiki/3.-Mutant-schemata

Shows how using a conditional (ternary) operator instead of an if statement avoids scope issues. This approach is chosen based on the type of SyntaxNode being mutated.

```csharp
int i = Environment.GetEnvironmentVariable("ActiveMutation") == "1" ? 0 : 99;
return i;
```

--------------------------------

### Ignore methods option in stryker-config.json

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/ignore-mutations.md

Configure Stryker.NET to ignore specific method calls using glob patterns. This only ignores mutations inside the method calls, not the method declarations.

```json
"stryker-config": {
    "ignore-methods": [
        "*Log", // Ignores all methods ending with Log
        "Console.Write*", // Ignores all methods starting with Write in the class Console
        "*Exception.ctor" // Ignores all exception constructors
    ]
}
```

--------------------------------

### Ignore specific LINQ expressions in stryker-config

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Configures Stryker to ignore specific LINQ expressions by listing their mutation names under the ignore-mutations array. Mutants of ignored types will not be tested and will appear as 'Ignored' in reports.

```json
"stryker-config": {
    "ignore-mutations": [
        "linq.First",
        "linq.Sum"
    ]
}
```

--------------------------------

### Mutate a specific span of lines with dotnet stryker -m

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/configuration.md

Use this command to mutate only a specific span of lines (from line 10 to line 100) within a file. The span is defined by the indices of the first and last character, and the pattern must be quoted.

```bash
dotnet stryker -m "MyFolder/MyService.cs{10..100}"
```

--------------------------------

### Collection expression mutation: replace empty collection with default

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates `[]` to `[default]` by replacing an empty collection expression with one containing the default value.

```csharp
[]
```

```csharp
[default]
```

--------------------------------

### Collection expression mutation: replace non-empty collection with empty

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates `[1, 2, 3]` to `[]` by replacing a non-empty collection expression with an empty one.

```csharp
[1, 2, 3]
```

```csharp
[]
```

--------------------------------

### Null-coalescing operator mutation: swap operands

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates `a ?? b` to `b ?? a` by swapping the left and right operands of the null-coalescing operator.

```csharp
a ?? b
```

```csharp
b ?? a
```

--------------------------------

### Ignore mutations option in stryker-config.json

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/ignore-mutations.md

Configure Stryker.NET to ignore all occurrences of specific mutation types. The option accepts an array of mutation type names, such as "string".

```json
"stryker-config": {
    "ignore-mutations": [
        "string"
    ]
}
```

--------------------------------

### Conditional operator mutation: replace condition with false

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates `x ? a : b` to `false ? a : b` by replacing the condition with the boolean literal `false`.

```csharp
x ? a : b
```

```csharp
false ? a : b
```

--------------------------------

### Conditional operator mutation: replace condition with true

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates `x ? a : b` to `true ? a : b` by replacing the condition with the boolean literal `true`.

```csharp
x ? a : b
```

```csharp
true ? a : b
```

--------------------------------

### Null-coalescing operator mutation: replace with left operand

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates `a ?? b` to `a` by removing the right operand and keeping only the left operand.

```csharp
a ?? b
```

```csharp
a
```

--------------------------------

### Null-coalescing operator mutation: replace with right operand

Source: https://github.com/stryker-mutator/stryker-net/blob/master/docs/mutations.md

Mutates `a ?? b` to `b` by removing the left operand and keeping only the right operand.

```csharp
a ?? b
```

```csharp
b
```
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