Terratest fails with Terragrunt v0.85.0+ due to deprecated --terragrunt-non-interactive flag

[matthewgulliver]

Describe the bug
Terratest fails when running tests with Terragrunt v0.85.0 or later due to the use of the deprecated --terragrunt-non-interactive flag, which was replaced with --non-interactive as part of Terragrunt's CLI redesign.

To Reproduce
Steps to reproduce the behavior:

1. Install Terragrunt v0.85.0 or later
2. Run any terratest test that uses terragrunt as the TerraformBinary
3. Observe the failure

terraformOptions := terraform.WithDefaultRetryableErrors(t, &terraform.Options{
    TerraformDir:    "../examples/terragrunt-example",
    TerraformBinary: "terragrunt",
})

terraform.Apply(t, terraformOptions) // This will fail

Expected behavior
Tests should run successfully with modern Terragrunt versions.

Actual behavior
Tests fail with error:

Error: Failed to parse command-line flags
│ 
│ flag provided but not defined: -terragrunt-non-interactive

Terminal output

TestTerragruntExample 2025-09-09T17:07:03+10:00 logger.go:67: time=2025-09-09AEST17:07:03+10:00 level=stderr tf-path=terraform msg=│ Error: Failed to parse command-line flags
TestTerragruntExample 2025-09-09T17:07:03+10:00 logger.go:67: time=2025-09-09AEST17:07:03+10:00 level=stderr tf-path=terraform msg=│ 
TestTerragruntExample 2025-09-09T17:07:03+10:00 logger.go:67: time=2025-09-09AEST17:07:03+10:00 level=stderr tf-path=terraform msg=│ flag provided but not defined: -terragrunt-non-interactive

Versions

• Terratest version: Latest (main branch - commit a4af63b)
• Terragrunt version: v0.86.2
• Terraform version: v1.13.1
• Go version: v1.24.2
• Environment details: Ubuntu 24.04.2 LTS

Additional context
This issue is caused by Terragrunt's CLI redesign that deprecated all --terragrunt-* prefixed flags in version 0.85.0 (released Aug 15, 2025). The --terragrunt-non-interactive flag was replaced with --non-interactive.

• Issue terratest and terragrunt 0.85 onwards #1586 identifies this exact problem:

Also:

terratest/modules/terraform/cmd.go

Line 58 in 1ce1b74

args = append(args, "--terragrunt-non-interactive")

That flag got deprecated removed in v0.85.

Originally posted by @tgeijg in #1586

• No existing PRs address this issue in Terratest or Terragrunt repos

Related:

• Official Terragrunt CLI redesign: https://terragrunt.gruntwork.io/docs/migrate/cli-redesign/
• Related issue: terratest and terragrunt 0.85 onwards #1586 (confirmed our problem, no solution provided)
• Official deprecation schedule: Road to 1.0 Deprecated Feature Removal Schedule terragrunt#3535
• Official CLI redesign RFC: CLI Redesign terragrunt#3445

Root Cause
The issue is in /modules/terraform/cmd.go line 59:

args = append(args, "--terragrunt-non-interactive")  // This flag no longer exists

Proposed Solution
Update to use the new flag:

args = append(args, "--non-interactive")  // Modern Terragrunt flag