SpecFlow’s behavior can be configured extensively. How to configure SpecFlow depends on the version of SpecFlow you are using.

SpecFlow 3.x

Starting with SpecFlow 3, you can use the specflow.json file to configure it. It is mandatory for .NET Core projects and it is recommended for .NET Framework projects.
When using the .NET Framework, you can still use the app.config file, as with earlier versions of SpecFlow.

If both the specflow.json and app.config files are available in a project, specflow.json takes precedence.

SpecFlow 2.x

SpecFlow 2 is configured in your standard .NET configuration file, app.config, which is automatically added to your project. This method is not supported by .NET Core, and SpecFlow 2 does not include .NET Core support.

We recommend using specflow.json in new projects.

Configuration Options

Both configuration methods use the same options and general structure. The only difference is that SpecFlow 2 only uses the app.config file (XML) and SpecFlow 3 requires the specflow.json file (JSON) for .NET Core projects.

Configuration examples

The following 2 examples show the same option defined in the specflow.json and app.config in formats:

specflow.json example:

  "language": {
    "feature": "de-AT"

app.config example:

<?xml version="1.0" encoding="utf-8"?>
    <section name="specFlow" type="TechTalk.SpecFlow.Configuration.ConfigurationSectionHandler, TechTalk.SpecFlow" />
    <language feature="de-AT" />

You can find more examples in the sample projects for SpecFlow.

Default Configuration

All SpecFlow configuration options have a default setting. Simple SpecFlow projects may not require any further configuration.

Configuring Your Unit Test Provider

SpecFlow 3

Yu can only configure your unit provider by adding the corresponding packages to your project. You will therefore need to add one of the following NuGet packages to your project to configure the unit test provider:

  • SpecRun.SpecFlow-3.3.0
  • SpecFlow.xUnit
  • SpecFlow.MsTest
  • SpecFlow.NUnit

Note: Make sure you do not add more than one of the unit test plugins to your project. If you do, an error message will be displayed.

SpecFlow 2

SpecFlow 2 is configured using the app.config file (Full Framework only). Enter your unit test provider in the unitTestProvider element in the specflow section, e.g.:

    <unitTestProvider name="MsTest" />

Configuration Elements

The same configuration elements are available in both the XML (app.config) and JSON (specflow.json) formats.


Use this section to define the default language for feature files and other language-related settings. For more details on language settings, see Feature Language.

Attribute Value Description
feature culture name (“en-US”) The default language of feature files added to the project. We recommend using specific culture names (e.g.: “en-US”) rather than generic (neutral) cultures (e.g.: “en”).
Default: en-US
tool empty or culture name Specifies the language that SpecFlow uses for messages and tracing. Uses the default feature language if empty and that language is supported; otherwise messages are displayed in English. (Note: Only English is currently supported.)
Default: empty


Use this section to define the culture for executing binding methods and converting step arguments. For more details on language settings, see Feature Language.

Attribute Value Description
name culture name (“en-US”) Specifies the culture to be used to execute binding methods and convert step arguments. If not specified, the feature language is used.
Default: not specified


Use this section to define unit test generation options.

Attribute Value Description
allowDebugGeneratedFiles true/false By default, the debugger is configured to step through the generated code. This helps you debug your feature files and bindings (see Debugging Tests). Disabled this option by setting this attribute to “true”.
Default: false
allowRowTests true/false Determines whether "row tests" should be generated for scenario outlines. This setting is ignored if the unit test framework does not support row based testing.
Default: true


Use this section to specify various test execution options.

Attribute Value Description
dependencies custom dependencies Specifies custom dependencies for the SpecFlow runtime. See Plugins for details.
Default: not specified
missingOrPendingStepsOutcome Inconclusive/Ignore/Error Determines how SpecFlow behaves if a step binding is not implemented or pending. See Test Result.
Default: Inconclusive
obsoleteBehavior None/Warn/Pending/Error how SpecFlow behaves if a step binding is marked with [Obsolete] attribute.
Default: Warn
stopAtFirstError true/false Determines whether the execution should stop when encountering the first error, or whether it should attempt to try and match subsequent steps (in order to detect missing steps).
Default: false


Use this section to determine the SpecFlow trace output.

Attribute Value Description
traceSuccessfulSteps true/false Determines whether SpecFlow should trace successful step binding executions.
Default: true
traceTimings true/false Determines whether SpecFlow should trace execution time of the binding methods (only if the execution time is longer than the minTracedDuration value).
Default: false
minTracedDuration TimeSpan (0:0:0.1) Specifies a threshold for tracing the binding execution times.
Default: 0:0:0.1 (100 ms)
stepDefinitionSkeletonStyle RegexAttribute/MethodNameUnderscores/MethodNamePascalCase/MethodNameRegex Specifies the default step definition style.
Default: RegexAttribute


This section can be used to configure additional assemblies that contain external binding assemblies. The assembly of the SpecFlow project (the project containing the feature files) is automatically included. The binding assemblies must be placed in the output folder (e.g. bin/Debug) of the SpecFlow project, for example by adding a reference to the assembly from the project.

The following example registers an additional binding assembly (MySharedBindings.dll).

specflow.json example:

    "stepAssemblies": [
        { "assembly": "MySharedBindings" }

app.config example:

    <stepAssembly assembly="MySharedBindings" />

The <stepAssemblies> can contain multiple <stepAssembly> elements (one for each assembly), with the following attributes.

Attribute Value Description
assembly assembly name The name of the assembly containing bindings.