Expressions_In_Cucumber_BDD

Tutorial 13​​ ​​ ​​ Expressions​​ in Cucumber​​ BDD

What you will Learn :

  • Backgound

  • Cucumber Expressions

  • Capture group

  • Quantifiers in regular expressions​​ 

Backgound

Cucumber supports 2 types of expressions:​​ 
1) Cucumber Expressions and​​ 
2) Regular Expressions​​ 

Cucumber Expressions

There​​ are certain rules for defining cucumber expressions:
Rule#1)​​ 

By default, the step definition file will generate ONLY cucumber expressions. To understand this​​ rule, let us refer the below feature file

Below is the corresponding step definition for each step​​ in the feature file.​​ 

If you notice below, the cucumber expressions {string} and {int} are automatically​​ getting​​ generated​​ by default​​ 

Let us add one new step in our feature file

Save the file and run it.

The console shows us the missing implementation. Notice again that cucumber expressions {string} and {int} got generated by default

Rule#2)​​ 

We can also use regular expressions​​ in step definition​​ file.​​ We​​ cannot​​ mix both expressions​​ (cucumber and regular)​​ in a​​ single​​ step definition​​ method.​​ 

To understand this rule, let us replace cucumber expression {int} with regular expression (\\d+) in line number 14.​​ 

So, in the same method, we have a mix of cucumber expression {string} and regular expression (\\d+)

Save the file

Run the feature file

Note below. There is an exception in console. So we cannot have a mix of both the expressions in a method

Rule#3)​​ 

We can mix regular expressions and cucumber expressions in a step definition file.​​ This means that, in one step definition method we can have cucumber expression and in another method we can have regular expression.​​ 

To understand this rule,​​ see below. Use regular expressions for method in line 14 and use cucumber expression for method in line 19

Save the file

Run the feature file

Notice the console o/p below. There is no error this time

 ​​​​ 

Capture group

The round brackets ( ) are capture groups and within them is the range of the group. So in the below method, the ranges are .* and d+

The dot matches any character, and the star allows the dot to be repeated any number of times, including zero.

\d is a digit (a character in the range 0-9), and + means 1 or more times. So, \d+ is 1 or more digits.

Quantifiers in regular expressions

Quantifier means how many times a character needs to be occurred.​​ There are 4 types of quantifiers in regular expressions:​​ 

plus +
asterisk *
question mark ?
total number of occurences {n}

Below is the brief description/example of above 4 quantifiers:​​ 

([0-9]+)

This means the digits 0 to 9 can appear once or more than once​​ 

([0-9]*)

This means the digits 0 to 9 can appear zero or more

([0-9]?)

This means the digits 0 to 9 can appear zero or once

([0-9]{3})

This means, between 0-9, generate 3 digits,​​ example: 000, 131, 610, 418,,​​ etc

You can refer the website for further details and examples
https://www.regular-expressions.info/refrepeat.html​​ 

Thank you​​ for reading!

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