Consider Known Value and Type Plan Checks for Resource Attributes and Output Values

[bendbennett]

terraform-plugin-testing version

v.1.6.0

Use cases

The plancheck package within terraform-plugin-testing has plan checks for the following:

• ExpectEmptyPlan
• ExpectNonEmptyPlan
• ExpectNullOutputValue
• ExpectNullOutputValueAtPath
• ExpectResourceAction
• ExpectSensitiveValue
• ExpectUnknownOutputValue
• ExpectUnknownOutputValueAtPath
• ExpectUnknownValue

Being able to assert that resource attributes, and output values in the plan have a known type and value is a use-case that is not yet catered for in the existing plan checks.

Attempted solutions

The only option currently available to provider developers who wish to assert that a resource attribute, or an output value has a known value and type is to implement custom plan checks using the plancheck.PlanCheck interface.

Proposal

The proposal is to

• Add plan checks for ExpectKnownValue, ExpectKnownOutputValue, and ExpectKnownOutputValueAtPath
• Add a KnownValue interface and types implementing this interface which can be used within the known value plan checks to assert that a resource attribute, or output value has a specified type and value.

type KnownValue interface {
	Equal(other any) bool
}

var _ KnownValue = stringValue{}

type stringValue struct {
	value string
}

func (v stringValue) Equal(other any) bool {
	otherVal, ok := other.(string)

	if !ok {
		return false
	}

	if otherVal != v.value {
		return false
	}

	return true
}

func StringValue(value string) stringValue {
	return stringValue{
		value: value,
	}
}

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