Demystifying Behave Step Files: Mastering Default Matcher Strategy

As a seasoned Behave user, you’re likely familiar with the concept of step files and the importance of specifying a matcher strategy. But have you ever wondered what happens when you forget to include the ‘use_step_matcher’ statement in your step file? Fear not, dear reader, for we’re about to dive into the world of default matcher strategies and explore how to force them to work in your favor.

What is a Matcher Strategy, Anyway?

In Behave, a matcher strategy is a crucial component that helps the framework determine how to match step definitions with the actual steps in your feature files. Think of it as a clever algorithm that ensures your tests run smoothly and accurately. There are several matcher strategies available in Behave, including:

• exact: Matches steps exactly, character for character.
• re: Matches steps using regular expressions.
• normalize: Matches steps after normalizing whitespace and converting to lowercase.
• difflib: Matches steps using the difflib library, which provides more flexibility than exact matching.

By default, Behave uses the ‘exact’ matcher strategy, which can be limiting in certain scenarios. That’s where the ‘use_step_matcher’ statement comes in – allowing you to specify a custom matcher strategy for your step files.

The ‘use_step_matcher’ Statement: A Quick Refresher

The ‘use_step_matcher’ statement is a simple yet powerful directive that tells Behave which matcher strategy to use for a particular step file. The basic syntax looks like this:

# -- *use_step_matcher*: re
from behave import *

In this example, the ‘re’ matcher strategy is specified, which enables regular expression matching for the step file. But what happens if you omit this statement entirely?

Falling Back to the Default Matcher Strategy

When a step file lacks the ‘use_step_matcher’ statement, Behave reverts to its default matcher strategy – which is ‘exact’ matching. This means that Behave will attempt to match steps exactly, character for character, without any fuzziness or flexibility.

While ‘exact’ matching can be suitable for simple scenarios, it may lead to issues when working with more complex step definitions or feature files. So, how can you force the default matcher strategy to work in your favor?

Forcing the Default Matcher Strategy

One approach is to explicitly specify the ‘exact’ matcher strategy in your step file, like this:

# -- *use_step_matcher*: exact
from behave import *

By doing so, you’re telling Behave to use the default matcher strategy, ensuring that your steps are matched exactly.

An Alternative Approach: Configuring Behave

Another way to force the default matcher strategy is by configuring Behave itself. You can do this by creating a `behave.ini` file in the root of your project, with the following contents:

[behave]
matcher=exact

This configuration tells Behave to use the ‘exact’ matcher strategy as the default for all step files in your project.

Best Practices for Working with Matcher Strategies

To get the most out of Behave’s matcher strategies, follow these best practices:

1. Specify a matcher strategy explicitly: Avoid relying on the default matcher strategy; instead, specify the desired matcher strategy for each step file using the ‘use_step_matcher’ statement.
2. Choose the right matcher strategy: Select a matcher strategy that suits your project’s needs. For example, if you’re working with complex step definitions, the ‘re’ or ‘difflib’ matcher strategy might be a better fit.
3. Keep your step definitions concise: Craft step definitions that are clear, concise, and easy to match. This will help reduce the complexity of your feature files and improve overall test maintainability.
4. Test thoroughly: Verify that your tests are running as expected by executing them with different matcher strategies. This will help you identify potential issues and optimize your test suite.

Conclusion

In conclusion, mastering Behave’s matcher strategies is crucial for writing effective and maintainable tests. By understanding how to force the default matcher strategy and configuring Behave to your needs, you’ll be better equipped to tackle complex testing scenarios. Remember to follow best practices, keep your step definitions concise, and test thoroughly to ensure your tests run smoothly and accurately.

Matcher Strategy	Description
exact	Matches steps exactly, character for character.
re	Matches steps using regular expressions.
normalize	Matches steps after normalizing whitespace and converting to lowercase.
difflib	Matches steps using the difflib library, which provides more flexibility than exact matching.

Now, go forth and conquer the world of Behave step files with confidence!

Frequently Asked Question

Get your questions answered about Behave step files and default matcher strategy!