feat(pactwritemode): allow user to set pact write mode.Fixes #30

Author: mefellows

Diff for: README.md

@@ -452,6 +452,26 @@ publishing or retrieving Pact files to/from a Pact Broker:
 * `BrokerUsername` - the username for Pact Broker basic authentication.
 * `BrokerPassword` - the password for Pact Broker basic authentication.
 
+### Splitting tests across multiple files
+
+Pact tests tend to be quite long, due to the need to be specific about request/response payloads. Often times it is nicer to be able to split your tests across multiple files for manageability.
+
+You have two options to achieve this feat:
+
+1. Set `PactFileWriteMode` to `"update"` when creating a `Pact` struct:
+
+    This will allow you to have multiple independent tests for a given Consumer-Provider pair, without it clobbering previous interactions.
+
+    See this [PR](https://github.com/pact-foundation/pact-js/pull/48) for background.
+
+    _NOTE_: If using this approach, you *must* be careful to clear out existing pact files (e.g. `rm ./pacts/*.json`) before you run tests to ensure you don't have left over requests that are no longer relevent.
+
+1. Create a Pact test helper to orchestrate the setup and teardown of the mock service for multiple tests.
+
+    In larger test bases, this can reduce test suite time and the amount of code you have to manage.
+
+    See the JS [example](https://github.com/tarciosaraiva/pact-melbjs/blob/master/helper.js) and related [issue](https://github.com/pact-foundation/pact-js/issues/11) for more.
+
 ### Output Logging
 
 Pact Go uses a simple log utility ([logutils](https://github.com/hashicorp/logutils))

Diff for: dsl/mock_service.go

@@ -22,6 +22,14 @@ type MockService struct {
 
 	// Provider name.
 	Provider string
+
+	// PactFileWriteMode specifies how to write to the Pact file, for the life
+	// of a Mock Service.
+	// "overwrite" will always truncate and replace the pact after each run
+	// "update" will append to the pact file, which is useful if your tests
+	// are split over multiple files and instantiations of a Mock Server
+	// See https://github.com/realestate-com-au/pact/blob/master/documentation/configuration.md#pactfile_write_mode
+	PactFileWriteMode string
 }
 
 // call sends a message to the Pact service
@@ -84,16 +92,22 @@ func (m *MockService) Verify() error {
 // WritePact writes the pact file to disk.
 func (m *MockService) WritePact() error {
 	log.Println("[DEBUG] mock service write pact")
+
 	if m.Consumer == "" || m.Provider == "" {
 		return errors.New("Consumer and Provider name need to be provided")
 	}
-	pact := map[string]map[string]string{
+	if m.PactFileWriteMode == "" {
+		m.PactFileWriteMode = "overwrite"
+	}
+
+	pact := map[string]interface{}{
 		"consumer": map[string]string{
 			"name": m.Consumer,
 		},
 		"provider": map[string]string{
 			"name": m.Provider,
 		},
+		"pactFileWriteMode": m.PactFileWriteMode,
 	}
 
 	url := fmt.Sprintf("%s/pact", m.BaseURL)

Diff for: dsl/pact.go

@@ -48,6 +48,14 @@ type Pact struct {
 	// Defaults to `<cwd>/pacts`.
 	PactDir string
 
+	// PactFileWriteMode specifies how to write to the Pact file, for the life
+	// of a Mock Service.
+	// "overwrite" will always truncate and replace the pact after each run
+	// "update" will append to the pact file, which is useful if your tests
+	// are split over multiple files and instantiations of a Mock Server
+	// See https://github.com/realestate-com-au/pact/blob/master/documentation/configuration.md#pactfile_write_mode
+	PactFileWriteMode string
+
 	// Specify which version of the Pact Specification should be used (1 or 2).
 	// Defaults to 2.
 	SpecificationVersion int
@@ -192,9 +200,10 @@ func (p *Pact) WritePact() error {
 	p.Setup(true)
 	log.Printf("[DEBUG] pact write Pact file")
 	mockServer := MockService{
-		BaseURL:  fmt.Sprintf("http://%s:%d", p.Host, p.Server.Port),
-		Consumer: p.Consumer,
-		Provider: p.Provider,
+		BaseURL:           fmt.Sprintf("http://%s:%d", p.Host, p.Server.Port),
+		Consumer:          p.Consumer,
+		Provider:          p.Provider,
+		PactFileWriteMode: p.PactFileWriteMode,
 	}
 	err := mockServer.WritePact()
 	if err != nil {