feat(test-structure): add save test data if dne

[bt-macole]

Description

SaveTestData is a powerful feature. But with great power comes great responsibility. If a user is not careful, this feature can cause unintended side effects including duplicating resources and overwriting state.

Adding support for only saving if a file does not exists prevent overwriting contents and provides terratest users protection from themselves.

resolves #1318

Adds SaveTerraformOptionsIfNotPresent and updates SaveTestData to include an additional overwrite bool attribute.

This change is backwards compatible.

Read the Gruntwork contribution guidelines.

• Update the docs.
• Run the relevant tests successfully, including pre-commit checks.
• Include release notes. If this PR is backward incompatible, include a migration guide.

Release Notes (draft)

Added / Removed / Updated [X].

Added SaveTerraformOptionsIfNotPresent

[denis256]

modules/test-structure/save_test_data.go:203:13: cannot use t (variable of type "github.com/gruntwork-io/terratest/modules/testing".TestingT) as type string in argument to t.Fatalf

[bt-macole]

modules/test-structure/save_test_data.go:203:13: cannot use t (variable of type "github.com/gruntwork-io/terratest/modules/testing".TestingT) as type string in argument to t.Fatalf

fixed:

--- PASS: TestSaveAndLoadTestData (0.00s)
PASS
ok      github.com/gruntwork-io/terratest/modules/test-structure        0.587s

[bt-macole]

@denis256 anything else needed here? not urgent, but we'd like to start using this feature in some of our test suite to avoid some accidental duplicated resources.

[denis256]

Hello,
the biggest concern is that PR doesn't have any test which will validate

$ grep -irn "SaveTerraformOptionsIfNotPresent" .
./modules/test-structure/save_test_data.go:27:// SaveTerraformOptionsIfNotPresent serializes and saves TerraformOptions into the given folder if the file does not exist or the json is
./modules/test-structure/save_test_data.go:30:func SaveTerraformOptionsIfNotPresent(t testing.TestingT, testFolder string, terraformOptions *terraform.Options) {
$

Implementation of SaveTerraformOptionsIfNotPresent can be changed in the future, so it will not be only a call of SaveTestData and there will be no tests to validate that SaveTerraformOptionsIfNotPresent will continue to work as before

[bt-macole]

@denis256 great point. added a test to test that functionality directly as well as a test that ensures the original overwriting behavior of SaveTerraformOptions is unchanged.