How to fix Error: Test assertion failed in Terraform

When a test fails, Terraform displays the line number, the condition that failed, and the custom error_message. Write down the exact value that was received and what was expected. This will help you identify the root cause quickly.

Double-check your test assumptions. For example, if asserting resource.name == "expected-name", verify that your configuration actually produces "expected-name". Test your Terraform plan separately to see actual values:

terraform plan -json | grep -i name

Ensure you are comparing compatible types. A common error is comparing a boolean to a string: local.enabled == "true" will fail because the actual value is boolean true, not string "true". Fix this by removing quotes or using tostring():

# Wrong
assert {
  condition = local.enabled == "true"
}

# Correct
assert {
  condition = local.enabled == true
}

If your assert block references a resource that fails a validation, the assertion won't be reached. Make sure all values you're asserting on are actually computed. If using expect_failures, separate those from assert blocks:

# Bad: mixing expect_failures with assert on same resource
run "test" {
  expect_failures = [ var.name ]
  assert {
    condition = aws_instance.example.id != null  # Never evaluated
  }
}

# Good: separate test runs
run "expect_invalid" {
  expect_failures = [ var.name ]
}

run "assert_valid" {
  assert {
    condition = aws_instance.example.id != null
  }
}

Update your error_message to include the actual value received for better debugging:

assert {
  condition     = aws_instance.example.tags["Name"] == "prod-server"
  error_message = "Expected tag Name=prod-server but got ${aws_instance.example.tags["Name"]}"
}

Catch configuration syntax errors early before running tests. These tools should never fail in your pipeline:

terraform fmt -check .
terraform validate
terraform plan -out=tfplan
terraform test