Variables Expander for Cucumber Steps

A lifesaver expander for cucumber/godog because, sometimes, you have to use variables in your steps.

Prerequisites

• Go >= 1.16

Install

go get github.com/godogx/expandvars

Usage

Initiate a new StepExpander with expandvars.NewStepExpander() then add it to ScenarioInitializer by calling StepExpander.RegisterContext(*testing.T, *godog.ScenarioContext)

package main

import (
    "fmt"
    "math/rand"
    "strings"
    "testing"

    "github.com/cucumber/godog"
    "github.com/godogx/expandvars"
    "github.com/stretchr/testify/assert"
)

func TestIntegration(t *testing.T) {
    expander := expandvars.NewStepExpander(
        strings.NewReplacer("$TO", "Berlin"),
        expandvars.Pairs{
            "HUSBAND": "John",
        },
        func() expandvars.Pairs {
            return expandvars.Pairs{
                "RAND": fmt.Sprintf("%d", rand.Int63()),
            }
        },
        expandvars.BeforeScenario(func() expandvars.Pairs {
            return expandvars.Pairs{
                "SCENARIO_RAND": fmt.Sprintf("%d", rand.Int63()),
            }
        }),
        func(s string) string {
            return strings.ReplaceAll(s, "$FROM", "Paris")
        },
        expandvars.Expander(func(s string) string {
            return strings.ReplaceAll(s, "$TRANSPORT", "by bus")
        }),
        // OS env vars.
        expandvars.EnvExpander,
    )

    suite := godog.TestSuite{
        Name: "Integration",
        ScenarioInitializer: func(ctx *godog.ScenarioContext) {
            expander.RegisterContext(ctx)
        },
        Options: &godog.Options{
            Strict:    true,
            Randomize: rand.Int63(),
        },
    }

    // Run the suite.
}

In your tests, just use $VARIABLE_NAME in the step or the argument, like this:

    Scenario: var is replaced
        Given var NAME is replaced in step text: $NAME

        Then step text is:
        """
        map var NAME is replaced in step text: John
        """

        Given var NAME is replaced in step argument (string)
        """
        NAME=$NAME
        """

        Then step argument is a string:
        """
        NAME=John
        """

        Given env var NAME is replaced in step argument (table)
            | col 1   | col 2 | col 3   |
            | value 1 | $NAME | value 3 |

        Then step argument is a table:
            | col 1   | col 2 | col 3   |
            | value 1 | John  | value 3 |

    Scenario: .github files
        Then there should be only these files in "$TEST_DIR/.github":
        """
        - workflows:
            - golangci-lint.yaml
            - test.yaml
        """

Expanders

The expanders could be any of these:

1. A Replacer interface

type Replacer interface {
    Replace(string) string
}

2. A Replacer func(string) string function.
   
   For example, you could use os.ExpandEnv or its alias expandvars.EnvExpander

3. A map or vars (without the $) map[string]string

var _ = expandvars.NewStepExpander(expandvars.Pairs{
    "HUSBAND": "John",
    "WIFE":    "Jane",
})

4. A provider that provides a map of vars (without the $) map[string]string. The provider will be called every step.

var _ = expandvars.NewStepExpander(func() expandvars.Pairs {
    return map[string]string{
        "RAND": fmt.Sprintf("%d", rand.Int63()),
    }
})

5. A BeforeScenario provides a map of vars (without the $) map[string]string. The provider will be called only once before every scenario.

Note: If you need expandvars.EnvExpander or os.ExpandEnv, put it in the end of the chain. Because it replaces not-found vars with empty strings, other expanders won't have a chance to do their jobs if you put it in the beginning.