Terraform Provider Design

Terraform Provider Design

Overview

This skill guides Terraform provider development using Test-Driven Development (TDD) following HashiCorp's official best practices. It supports the complete RED-GREEN-REFACTOR cycle with parallel execution patterns for efficient provider development.

When to Use This Skill

Use this skill when:

• Creating a new Terraform provider from scratch
• Adding resources or data sources to an existing provider
• Implementing TDD workflows for provider development
• Designing provider architecture and schemas
• Writing acceptance tests for provider resources
• Reviewing provider code for HashiCorp compliance

Core TDD Workflow

The RED-GREEN-REFACTOR Cycle

Provider development follows strict TDD phases executed in parallel where possible:

🔴 RED Phase: Write failing acceptance tests

• Define resource/data source behavior through tests
• Write Terraform configuration fixtures
• Verify tests fail for the right reasons

🟢 GREEN Phase: Write minimal CRUD code

• Implement simplest code to pass tests
• Use hardcoded values initially if needed
• Focus on making tests pass quickly

🔄 REFACTOR Phase: Improve implementation

• Add real API integration
• Enhance error handling
• Optimize code quality
• Keep all tests passing

Parallel Execution Pattern

Execute multiple TDD cycles concurrently:

# RED PHASE - Write multiple failing tests in parallel
Write("internal/provider/instance_resource_test.go")
Write("internal/provider/network_resource_test.go")
Write("internal/provider/user_data_source_test.go")
Bash("TF_ACC=1 go test -v -timeout 120m ./internal/provider/")

# GREEN PHASE - Implement minimal CRUD in parallel
Write("internal/provider/instance_resource.go")
Write("internal/provider/network_resource.go")
Write("internal/provider/user_data_source.go")
Bash("TF_ACC=1 go test -v -timeout 120m ./internal/provider/")

# REFACTOR PHASE - Improve implementations in parallel
Edit("internal/provider/instance_resource.go")
Edit("internal/provider/network_resource.go")
Edit("internal/provider/user_data_source.go")
Bash("TF_ACC=1 go test -v -timeout 120m ./internal/provider/")

Getting Started

Project Initialization

Create a new provider project:

# Initialize Go module
go mod init github.com/yourusername/terraform-provider-{name}

# Add required dependencies
go get github.com/hashicorp/terraform-plugin-framework
go get github.com/hashicorp/terraform-plugin-go
go get github.com/hashicorp/terraform-plugin-log
go get github.com/hashicorp/terraform-plugin-testing

# Create directory structure
mkdir -p internal/provider examples/{provider,resources,data-sources} docs

Provider Bootstrap Template

See assets/provider_template.go for a complete provider initialization example.

Provider Structure

Standard Directory Layout

terraform-provider-{name}/
├── internal/
│   └── provider/
│       ├── provider.go              # Provider definition
│       ├── provider_test.go         # Provider tests
│       ├── resource_*.go            # Resource implementations
│       ├── resource_*_test.go       # Resource acceptance tests
│       ├── data_source_*.go         # Data source implementations
│       └── data_source_*_test.go    # Data source acceptance tests
├── examples/
│   ├── provider/                    # Provider configuration examples
│   ├── resources/                   # Resource examples
│   └── data-sources/                # Data source examples
├── docs/                            # Generated documentation
├── main.go                          # Provider binary entry point
├── go.mod                           # Go module dependencies
├── CHANGELOG.md                     # Version history
├── .goreleaser.yml                  # Release automation
└── GNUmakefile                      # Build and test commands

Design Principles

Follow HashiCorp's core design principles (see references/hashicorp_best_practices.md for details):

1. Single API Focus: One provider per API/service domain
2. Single Object per Resource: One API object per Terraform resource
3. Schema Alignment: Match underlying API unless it degrades UX
4. Import Support: All resources must support terraform import
5. Version Continuity: Maintain backward compatibility

Resource Design Workflow

Step 1: Define Resource Schema

Start with the schema that matches the underlying API:

func (r *InstanceResource) Schema(ctx context.Context, req resource.SchemaRequest, resp *resource.SchemaResponse) {
    resp.Schema = schema.Schema{
        MarkdownDescription: "Instance resource",
        Attributes: map[string]schema.Attribute{
            "id": schema.StringAttribute{
                Computed:            true,
                MarkdownDescription: "Instance identifier",
            },
            "name": schema.StringAttribute{
                Required:            true,
                MarkdownDescription: "Instance name",
            },
            "tags": schema.MapAttribute{
                Optional:            true,
                ElementType:         types.StringType,
                MarkdownDescription: "Resource tags",
            },
        },
    }
}

Step 2: Write Acceptance Test (RED)

Create failing test before implementation:

func TestAccInstanceResource(t *testing.T) {
    resource.Test(t, resource.TestCase{
        PreCheck:                 func() { testAccPreCheck(t) },
        ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
        Steps: []resource.TestStep{
            // Create and Read
            {
                Config: testAccInstanceResourceConfig("test"),
                Check: resource.ComposeAggregateTestCheckFunc(
                    resource.TestCheckResourceAttr("example_instance.test", "name", "test"),
                    resource.TestCheckResourceAttrSet("example_instance.test", "id"),
                ),
            },
            // ImportState
            {
                ResourceName:      "example_instance.test",
                ImportState:       true,
                ImportStateVerify: true,
            },
            // Update and Read
            {
                Config: testAccInstanceResourceConfig("test-updated"),
                Check: resource.ComposeAggregateTestCheckFunc(
                    resource.TestCheckResourceAttr("example_instance.test", "name", "test-updated"),
                ),
            },
        },
    })
}

Step 3: Minimal Implementation (GREEN)

Implement simplest CRUD to pass tests:

func (r *InstanceResource) Create(ctx context.Context, req resource.CreateRequest, resp *resource.CreateResponse) {
    var data InstanceResourceModel
    resp.Diagnostics.Append(req.Plan.Get(ctx, &data)...)
    if resp.Diagnostics.HasError() {
        return
    }

    // Minimal - hardcoded for now
    data.ID = types.StringValue("instance-123")

    resp.Diagnostics.Append(resp.State.Set(ctx, &data)...)
}

Step 4: Full Implementation (REFACTOR)

Add real API integration:

func (r *InstanceResource) Create(ctx context.Context, req resource.CreateRequest, resp *resource.CreateResponse) {
    var data InstanceResourceModel
    resp.Diagnostics.Append(req.Plan.Get(ctx, &data)...)
    if resp.Diagnostics.HasError() {
        return
    }

    // Real API call
    instance, err := r.client.CreateInstance(ctx, data.Name.ValueString())
    if err != nil {
        resp.Diagnostics.AddError(
            "Error Creating Instance",
            "Could not create instance: "+err.Error(),
        )
        return
    }

    data.ID = types.StringValue(instance.ID)
    resp.Diagnostics.Append(resp.State.Set(ctx, &data)...)
}

Naming Conventions

Follow HashiCorp naming standards:

Resources: Singular nouns with provider prefix

• Format: {provider}_{resource_name}
• Example: aws_instance, postgresql_database

Data Sources: Nouns (plural for collections)

• Format: {provider}_{data_source_name}
• Example: aws_availability_zones, azurerm_subnet

Attributes: Lowercase with underscores

• Single values: Singular nouns (instance_type)
• Collections: Plural nouns (security_group_ids)
• Booleans: Nouns describing what's enabled (auto_scaling_enabled)

Functions: Verbs without provider prefix

• Format: {verb}_{object}
• Example: parse_rfc3339, encode_base64

Testing Requirements

TestCase Structure - The Foundation

Every acceptance test is built around resource.TestCase, the Go struct that defines the complete test lifecycle.

📚 COMPLETE GUIDE: See references/testcase_structure.md for comprehensive TestCase documentation

Essential TestCase Fields

func TestAccResourceName(t *testing.T) {
    resource.Test(t, resource.TestCase{
        // Validate prerequisites
        PreCheck: func() { testAccPreCheck(t) },

        // Check Terraform version compatibility
        TerraformVersionChecks: []tfversion.TerraformVersionCheck{
            tfversion.SkipBelow(tfversion.Version1_8_0),
        },

        // Provider setup (REQUIRED)
        ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,

        // Verify cleanup after destroy (REQUIRED for resources)
        CheckDestroy: testAccCheckResourceDestroy,

        // Test steps (REQUIRED)
        Steps: []resource.TestStep{
            // Create, Import, Update, etc.
        },
    })
}

Key TestCase Fields:

• ✅ ProtoV6ProviderFactories (Required) - Provider factory map
• ✅ Steps (Required) - Array of test operations
• ✅ PreCheck (Recommended) - Environment validation
• ✅ CheckDestroy (Required for resources) - Cleanup verification
• ⚙️ TerraformVersionChecks (Optional) - Version constraints
• ⚙️ ErrorCheck (Optional) - Custom error handling

Acceptance Test Coverage

Every resource MUST test:

1. ✅ Create and Read operations
2. ✅ ImportState functionality
3. ✅ Update and Read operations
4. ✅ Delete operations with CheckDestroy
5. ✅ Drift detection with plan checks
6. ✅ Idempotency verification with ExpectEmptyPlan

📚 For complete TestCase structure details, see references/testcase_structure.md

📚 For comprehensive plan checks guidance, see references/plan_checks_guide.md

Testing Pattern Categories

HashiCorp recommends four core testing patterns (see Testing Patterns):

1. Basic Attribute Verification - Configuration applies, attributes persist with correct values
2. Update Tests - Resources correctly apply updates while maintaining state consistency
3. Import Mode Testing - Verify import behavior with ImportState: true
4. Error and Plan Expectations - Validate expected failures and plan outcomes

State Checks

State checks validate resource attributes in Terraform state after terraform apply. They execute during Lifecycle (config) mode and provide comprehensive attribute verification.

Key Characteristics:

• Multiple state checks can run with aggregated error reporting
• Cleanup executes even when checks fail
• Primarily for validating computed attributes

ExpectKnownValue - Verify Attribute Type and Value:

import (
    "github.com/hashicorp/terraform-plugin-testing/statecheck"
    "github.com/hashicorp/terraform-plugin-testing/tfjsonpath"
    "github.com/hashicorp/terraform-plugin-testing/knownvalue"
)

// Basic attribute verification
StateChecks: []statecheck.StateCheck{
    statecheck.ExpectKnownValue(
        "example_instance.test",
        tfjsonpath.New("name"),
        knownvalue.StringExact("test-instance"),
    ),
    statecheck.ExpectKnownValue(
        "example_instance.test",
        tfjsonpath.New("enabled"),
        knownvalue.Bool(true),
    ),
}

// Nested attribute with map key access
StateChecks: []statecheck.StateCheck{
    statecheck.ExpectKnownValue(
        "example_instance.test",
        tfjsonpath.New("tags").AtMapKey("environment"),
        knownvalue.StringExact("production"),
    ),
}

// Understanding tfjson Paths
// Paths specify exact locations within Terraform JSON data structures
// Supporting hierarchical navigation:

// Root-level attribute
tfjsonpath.New("name")

// Nested block attribute
tfjsonpath.New("configuration").AtMapKey("setting1")

// List element
tfjsonpath.New("items").AtSliceIndex(0)

// Complex nested structure
tfjsonpath.New("network").AtMapKey("subnets").AtSliceIndex(0).AtMapKey("cidr")

// Builder Methods:
// - AtMapKey(key) - Access map values or nested attributes
// - AtSliceIndex(index) - Access list or set elements

CompareValue - Track Attribute Changes Across Steps:

// Compare computed values across test steps
compareValuesSame := statecheck.CompareValue(compare.ValuesSame())

// First test step - capture initial value
{
    Config: testAccInstanceResourceConfig("test"),
    ConfigStateChecks: []statecheck.StateCheck{
        compareValuesSame.AddStateValue(
            "example_instance.test",
            tfjsonpath.New("computed_id"),
        ),
    },
}

// Second test step - verify value hasn't changed
{
    Config: testAccInstanceResourceConfig("test-updated"),
    ConfigStateChecks: []statecheck.StateCheck{
        compareValuesSame.AddStateValue(
            "example_instance.test",
            tfjsonpath.New("computed_id"),
        ),
    },
}

Known Value Types:

// Boolean values
knownvalue.Bool(true)

// String values
knownvalue.StringExact("exact-match")

// Numeric values
knownvalue.Int64Exact(42)
knownvalue.Float64Exact(3.14)

// Null and existence checks
knownvalue.Null()
knownvalue.NotNull()

// Collections
knownvalue.ListExact([]knownvalue.Check{
    knownvalue.StringExact("item1"),
    knownvalue.StringExact("item2"),
})

knownvalue.MapExact(map[string]knownvalue.Check{
    "key1": knownvalue.StringExact("value1"),
    "key2": knownvalue.Int64Exact(100),
})

knownvalue.SetExact([]knownvalue.Check{
    knownvalue.StringExact("elem1"),
    knownvalue.StringExact("elem2"),
})

Sensitive Value Verification (Terraform 1.4.6+):

// Verify attribute is marked sensitive
StateChecks: []statecheck.StateCheck{
    statecheck.ExpectSensitiveValue(
        "example_instance.test",
        tfjsonpath.New("api_key"),
    ),
}

State Check Best Practices:

• Validate computed attributes, not user-provided configuration
• Use ExpectKnownValue for exact value matching
• Use CompareValue to track consistency across test steps
• Use ExpectSensitiveValue for sensitive attributes
• Leverage JSON paths for nested attribute access

Plan Checks

Plan checks are critical for validating Terraform plan behavior. They inspect plan files at specific phases to ensure expected operations.

📚 COMPREHENSIVE GUIDE: See references/plan_checks_guide.md for complete documentation

Plan checks validate Terraform plan outcomes during test execution. They ensure configuration changes produce expected planning results.

Key Characteristics:

• Multiple checks per phase with aggregated error reporting
• Cleanup executes even when checks fail
• Available in Lifecycle (config) and Refresh test modes

Built-in Plan Check Functions:

import "github.com/hashicorp/terraform-plugin-testing/plancheck"

// ExpectEmptyPlan - Asserts no operations for apply
// Use when: Verifying idempotency or that updates produce no changes
ConfigPlanChecks: resource.ConfigPlanChecks{
    PreApply: []plancheck.PlanCheck{
        plancheck.ExpectEmptyPlan(),
    },
}

// ExpectNonEmptyPlan - Asserts at least one operation for apply
// Use when: Confirming configuration changes trigger updates
ConfigPlanChecks: resource.ConfigPlanChecks{
    PreApply: []plancheck.PlanCheck{
        plancheck.ExpectNonEmptyPlan(),
    },
}

Plan Check Example:

func TestAccInstanceResource_Idempotent(t *testing.T) {
    resource.Test(t, resource.TestCase{
        PreCheck:                 func() { testAccPreCheck(t) },
        ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
        Steps: []resource.TestStep{
            // Create
            {
                Config: testAccInstanceResourceConfig("test"),
                Check: resource.ComposeAggregateTestCheckFunc(
                    resource.TestCheckResourceAttr("example_instance.test", "name", "test"),
                ),
            },
            // Verify idempotency - no plan changes
            {
                Config: testAccInstanceResourceConfig("test"),
                ConfigPlanChecks: resource.ConfigPlanChecks{
                    PreApply: []plancheck.PlanCheck{
                        plancheck.ExpectEmptyPlan(),
                    },
                },
            },
        },
    })
}

Plan Check Best Practices:

• Use ExpectEmptyPlan() to verify idempotency after resource creation
• Use ExpectNonEmptyPlan() to confirm updates actually trigger changes
• Combine with drift detection tests to verify Read operations
• Available check types: General, Resource, Output, and Custom plan checks

Comprehensive Testing Example

Combining state checks, plan checks, and traditional checks:

func TestAccInstanceResource_Complete(t *testing.T) {
    compareID := statecheck.CompareValue(compare.ValuesSame())

    resource.Test(t, resource.TestCase{
        PreCheck:                 func() { testAccPreCheck(t) },
        ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
        Steps: []resource.TestStep{
            // Create and verify
            {
                Config: testAccInstanceResourceConfig("test"),
                Check: resource.ComposeAggregateTestCheckFunc(
                    resource.TestCheckResourceAttr("example_instance.test", "name", "test"),
                    resource.TestCheckResourceAttrSet("example_instance.test", "id"),
                ),
                ConfigStateChecks: []statecheck.StateCheck{
                    statecheck.ExpectKnownValue(
                        "example_instance.test",
                        tfjsonpath.New("name"),
                        knownvalue.StringExact("test"),
                    ),
                    compareID.AddStateValue(
                        "example_instance.test",
                        tfjsonpath.New("id"),
                    ),
                },
            },
            // Verify idempotency
            {
                Config: testAccInstanceResourceConfig("test"),
                ConfigPlanChecks: resource.ConfigPlanChecks{
                    PreApply: []plancheck.PlanCheck{
                        plancheck.ExpectEmptyPlan(),
                    },
                },
            },
            // Update and verify ID remains same
            {
                Config: testAccInstanceResourceConfig("test-updated"),
                Check: resource.ComposeAggregateTestCheckFunc(
                    resource.TestCheckResourceAttr("example_instance.test", "name", "test-updated"),
                ),
                ConfigStateChecks: []statecheck.StateCheck{
                    statecheck.ExpectKnownValue(
                        "example_instance.test",
                        tfjsonpath.New("name"),
                        knownvalue.StringExact("test-updated"),
                    ),
                    // Verify ID hasn't changed
                    compareID.AddStateValue(
                        "example_instance.test",
                        tfjsonpath.New("id"),
                    ),
                },
            },
        },
    })
}

Regression Testing Pattern

When fixing bugs, follow this workflow:

1. Create regression test - Write failing test that reproduces the bug
2. Commit test first - Commit shows problem independently verified
3. Implement fix - Subsequent commits fix the issue
4. Verify test passes - Confirms fix resolves the problem

This allows independent verification of problem reproduction before evaluating solutions

Test Helper Patterns

Create reusable test helpers for common operations:

Test Helpers File (internal/provider/test_helpers.go):

// createTestClient - Authenticate and return API client for tests
func createTestClient(t *testing.T) *APIClient {
    endpoint := os.Getenv("API_ENDPOINT")
    username := os.Getenv("API_USERNAME")
    password := os.Getenv("API_PASSWORD")

    if endpoint == "" || username == "" || password == "" {
        t.Fatalf("API credentials not set")
    }

    client, err := NewAPIClient(context.Background(), endpoint, username, password)
    if err != nil {
        t.Fatalf("Failed to create client: %v", err)
    }
    return client
}

// getResourceIDByName - Query API to get resource ID by name
func getResourceIDByName(t *testing.T, service, method, name string) string {
    client := createTestClient(t)
    body, err := client.CallAPI(context.Background(), service, method, name)
    if err != nil {
        t.Fatalf("Failed to get resource: %v", err)
    }

    var resource map[string]interface{}
    json.Unmarshal(body, &resource)
    return resource["id"].(string)
}

// verifyResourceDeleted - Poll API with exponential backoff to verify deletion
func verifyResourceDeleted(ctx context.Context, client *APIClient,
    service, method, id string, maxRetries int) (bool, error) {

    for i := 0; i < maxRetries; i++ {
        _, err := client.CallAPI(ctx, service, method, id)
        if err != nil {
            // Resource not found - successfully deleted
            return true, nil
        }
        time.Sleep(time.Duration(1<<i) * time.Second) // Exponential backoff
    }
    return false, fmt.Errorf("resource still exists after %d retries", maxRetries)
}

// generateUniqueTestName - Create timestamped unique test names
func generateUniqueTestName(prefix string) string {
    return fmt.Sprintf("%s-%d", prefix, time.Now().Unix())
}

CheckDestroy Pattern

Implement CheckDestroy to verify resource cleanup:

func testAccCheckResourceDestroy(s *terraform.State) error {
    client := createTestClient(&testing.T{})
    ctx := context.Background()

    for _, rs := range s.RootModule().Resources {
        if rs.Type != "example_resource" {
            continue
        }

        // Verify resource is deleted with exponential backoff
        deleted, err := verifyResourceDeleted(ctx, client,
            "ServiceName", "getMethod", rs.Primary.ID, 4)

        if !deleted {
            if err != nil {
                return fmt.Errorf("error checking deletion: %w", err)
            }
            return fmt.Errorf("resource %s still exists", rs.Primary.ID)
        }
    }
    return nil
}

// Add to TestCase
resource.Test(t, resource.TestCase{
    CheckDestroy: testAccCheckResourceDestroy,
    // ... rest of test
})

Drift Detection Test Pattern

Comprehensive drift detection using test helpers:

func TestAccResource_DriftDetection(t *testing.T) {
    name := generateUniqueTestName("test-drift")

    resource.Test(t, resource.TestCase{
        PreCheck: func() { testAccPreCheck(t) },
        ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
        Steps: []resource.TestStep{
            // Step 1: Create resource
            {
                Config: testAccResourceConfig(name, "initial-value"),
                Check: resource.ComposeAggregateTestCheckFunc(
                    resource.TestCheckResourceAttr("example_resource.test", "attr", "initial-value"),
                ),
            },
            // Step 2: Modify externally (drift)
            {
                PreConfig: func() {
                    client := createTestClient(t)
                    ctx := context.Background()

                    // Get resource ID by name
                    id := getResourceIDByName(t, "Service", "getMethod", name)

                    // Fetch full resource data
                    body, _ := client.CallAPI(ctx, "Service", "getMethod", name)
                    var resourceData map[string]interface{}
                    json.Unmarshal(body, &resourceData)

                    // Modify field externally (note: snake_case → camelCase mapping!)
                    resourceData["camelCaseField"] = "modified-value"
                    resourceData["id"] = id

                    // Update via API
                    client.CallAPI(ctx, "Service", "updateMethod", resourceData)

                    // Wait for eventual consistency
                    time.Sleep(2 * time.Second)
                },
                Config: testAccResourceConfig(name, "initial-value"),
                ConfigPlanChecks: resource.ConfigPlanChecks{
                    PreApply: []plancheck.PlanCheck{
                        plancheck.ExpectNonEmptyPlan(),
                    },
                },
            },
            // Step 3: Terraform restores desired state
            {
                Config: testAccResourceConfig(name, "initial-value"),
                Check: resource.ComposeAggregateTestCheckFunc(
                    resource.TestCheckResourceAttr("example_resource.test", "attr", "initial-value"),
                ),
            },
        },
    })
}

Important Drift Detection Notes:

• Field Name Mapping: APIs often use camelCase while Terraform uses snake_case (e.g., kernel_parameters → kernelParameters)
• Document Mappings: Create a mapping table in test_helpers.go for clarity
• Eventual Consistency: Add sleep after API modifications (typically 2s)
• UUID Lookup: Use test helper to get resource ID before modification

For comprehensive drift detection guidance, see references/drift_detection_guide.md

Running Tests

# Unit tests
go test -v ./...

# Acceptance tests
TF_ACC=1 go test -v -timeout 120m ./internal/provider/

# Parallel execution
TF_ACC=1 go test -v -parallel=4 -timeout 120m ./...

# Run specific test patterns
TF_ACC=1 go test -v -run "Drift" ./internal/provider/

# With detailed logging
TF_LOG=TRACE TF_ACC=1 go test -v ./internal/provider/

Quality Standards

• Pass Rate: 100% required
• Coverage: All CRUD operations
• Import: All resources importable
• Execution Time: <120m for full suite
• Parallel Tests: 4-8 concurrent recommended

Sensitive Data Handling

Recommended: Ephemeral Resources

For sensitive data like tokens or secrets:

// Use ephemeral resources (Plugin Framework only)
// Data not persisted in state

Alternative: Sensitive Flag

Mark sensitive attributes:

"api_key": schema.StringAttribute{
    Required:  true,
    Sensitive: true, // Prevents display in output
}

Note: Sensitive flag does NOT encrypt state files. Use remote backends with encryption at rest.

Documentation Generation

Generate provider documentation automatically:

go run github.com/hashicorp/terraform-plugin-docs/cmd/tfplugindocs generate

Ensure examples/ directory contains:

• provider/provider.tf - Provider configuration
• resources/{resource_name}/resource.tf - Resource examples
• data-sources/{data_source_name}/data-source.tf - Data source examples

Versioning

Follow Semantic Versioning (MAJOR.MINOR.PATCH):

MAJOR - Breaking changes:

• Removing/renaming resources or attributes
• Changing authentication patterns
• Incompatible type changes

MINOR - New features:

• Adding resources or attributes
• Deprecation warnings
• Compatible type changes

PATCH - Bug fixes only

Recommendation: Major versions no more than once per year

CI/CD and Tooling

Continuous Integration

Set up automated testing with GitHub Actions:

# .github/workflows/test.yml
name: Tests
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-go@v4
        with:
          go-version: "1.21"
      - run: go test -v -cover ./...
      - run: TF_ACC=1 go test -v -timeout 120m ./internal/provider/

Code Quality and Release

See references/ci_cd_patterns.md for:

• golangci-lint configuration
• GoReleaser setup for provider releases
• Pre-commit hooks
• Documentation generation automation

Testing Best Practices

Test Environment Setup

Create isolated test environments:

func testAccPreCheck(t *testing.T) {
    // Verify API credentials
    if v := os.Getenv("EXAMPLE_API_KEY"); v == "" {
        t.Fatal("EXAMPLE_API_KEY must be set for acceptance tests")
    }

    // Verify API endpoint
    if v := os.Getenv("EXAMPLE_API_ENDPOINT"); v == "" {
        t.Skip("EXAMPLE_API_ENDPOINT not set, skipping acceptance tests")
    }
}

Test Safety

CRITICAL: Use separate accounts/namespaces for testing:

• Prevents accidental production infrastructure changes
• Allows safe parallel test execution
• Enables test cleanup without risk

ID Attribute Requirement

For terraform-plugin-testing v1.5.0+, always add root-level id attribute:

"id": schema.StringAttribute{
    Computed:            true,
    MarkdownDescription: "Resource identifier",
},

Parallel Testing Configuration

# Run tests in parallel (recommended 4-8)
TF_ACC=1 go test -v -parallel=4 -timeout 120m ./...

# Run specific test
TF_ACC=1 go test -v -run TestAccExampleResource ./internal/provider/

Resources

Templates (assets/)

• provider_template.go - Provider initialization and configuration template
• main_template.go - Provider binary entry point template
• resource_template.go - Complete resource implementation template
• data_source_template.go - Data source implementation template
• acceptance_test_template.go - Acceptance test template with all required steps

References (references/)

Testing Fundamentals:

• testcase_structure.md - Complete TestCase structure, all fields, execution flow, and best practices
• plan_checks_guide.md - Comprehensive plan checks documentation with all types and patterns
• tdd_patterns.md - TDD workflows, test helpers, CheckDestroy, and test structures
• drift_detection_guide.md - External modification testing with three-step pattern

Implementation Patterns:

• api_client_patterns.md - API client architecture, authentication, retry logic, and error handling
• hashicorp_best_practices.md - Official HashiCorp design principles and standards
• ci_cd_patterns.md - CI/CD workflows, automation, tooling, and release management

Quick Reference

Provider Test Setup

var testAccProtoV6ProviderFactories = map[string]func() (tfprotov6.ProviderServer, error){
    "example": providerserver.NewProtocol6WithError(New("test")()),
}

func testAccPreCheck(t *testing.T) {
    // Verify required environment variables
}

State Check Functions

// Exact match
resource.TestCheckResourceAttr("example_instance.test", "name", "expected")

// Attribute exists
resource.TestCheckResourceAttrSet("example_instance.test", "id")

// Match between resources
resource.TestCheckResourceAttrPair("example_instance.test", "vpc_id", "example_vpc.test", "id")

// Combine checks
resource.ComposeAggregateTestCheckFunc(
    resource.TestCheckResourceAttr(...),
    resource.TestCheckResourceAttrSet(...),
)

Common Anti-Patterns to Avoid

❌ Skipping ImportState tests ❌ Skipping Drift tests ❌ Skipping CheckDestroy implementation ❌ Skipping idempotency tests with plan checks ❌ Using hardcoded test values (use generateUniqueTestName() instead) ❌ Incomplete CRUD testing ❌ Ignoring error cases ❌ Missing or outdated documentation ❌ Not testing state drift ❌ Tests dependent on external state ❌ Not verifying plan outcomes with ExpectEmptyPlan/ExpectNonEmptyPlan ❌ Using TestCheckResourceAttr for computed values (use StateChecks instead) ❌ Not tracking attribute consistency across test steps (use CompareValue) ❌ Missing sensitive attribute verification (use ExpectSensitiveValue) ❌ Not documenting field name mappings (snake_case vs camelCase) ❌ Missing test helper functions for repeated operations ❌ Not using exponential backoff for eventual consistency ❌ Duplicating client setup code across tests

Development Checklist

• Schema aligns with underlying API
• Resource supports import (ImportState tests)
• All CRUD operations tested
• CheckDestroy function implemented and working
• Test helper functions created (createTestClient, verifyResourceDeleted, etc.)
• Field name mappings documented (snake_case vs camelCase)
• Unique test names generated with timestamps
• State checks verify computed attributes (ExpectKnownValue)
• Attribute consistency tracked across steps (CompareValue)
• Idempotency verified with plan checks (ExpectEmptyPlan)
• Drift detection tests implemented with external modification
• Eventual consistency handled with exponential backoff
• Sensitive attributes verified (ExpectSensitiveValue)
• Error cases tested (ExpectError)
• Acceptance tests pass 100%
• Documentation generated
• CHANGELOG updated
• Examples provided
• Sensitive data handled properly
• Version follows semantic versioning
• Code follows HashiCorp conventions

Source: ForceInjection/domain-driven-design-skills — distributed by TomeVault.