makes DependencyMapper packit-internal

Signed-off-by: Forest Eckhardt <feckhardt@pivotal.io>

postal/init_test.go

@@ -10,7 +10,6 @@ import (
 func TestUnitPostal(t *testing.T) {
 	suite := spec.New("packit/postal", spec.Report(report.Terminal{}))
 	suite("Service", testService)
-	suite("DependencyMappings", testDependencyMappings)
 
 	suite.Run(t)
 }

postal/dependency_mappings.go → postal/internal/dependency_mappings.go

@@ -1,4 +1,4 @@
-package postal
+package internal
 
 import (
 	"fmt"

postal/dependency_mappings_test.go → postal/internal/dependency_mappings_test.go

@@ -1,12 +1,12 @@
-package postal_test
+package internal_test
 
 import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
 
-	"github.com/paketo-buildpacks/packit/postal"
+	"github.com/paketo-buildpacks/packit/postal/internal"
 	"github.com/sclevine/spec"
 
 	. "github.com/onsi/gomega"
@@ -16,13 +16,13 @@ func testDependencyMappings(t *testing.T, context spec.G, it spec.S) {
 	var (
 		Expect      = NewWithT(t).Expect
 		path        string
-		resolver    postal.DependencyMappingResolver
+		resolver    internal.DependencyMappingResolver
 		bindingPath string
 		err         error
 	)
 
 	it.Before(func() {
-		resolver = postal.NewDependencyMappingResolver()
+		resolver = internal.NewDependencyMappingResolver()
 		bindingPath, err = ioutil.TempDir("", "bindings")
 		Expect(err).NotTo(HaveOccurred())
 	})

postal/internal/init_test.go

@@ -0,0 +1,15 @@
+package internal_test
+
+import (
+	"testing"
+
+	"github.com/sclevine/spec"
+	"github.com/sclevine/spec/report"
+)
+
+func TestUnitPostalInternal(t *testing.T) {
+	suite := spec.New("packit/postal/internal", spec.Report(report.Terminal{}))
+	suite("DependencyMappings", testDependencyMappings)
+
+	suite.Run(t)
+}

postal/service.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/Masterminds/semver/v3"
 	"github.com/paketo-buildpacks/packit/cargo"
+	"github.com/paketo-buildpacks/packit/postal/internal"
 	"github.com/paketo-buildpacks/packit/vacation"
 )
 
@@ -38,7 +39,7 @@ type Service struct {
 func NewService(transport Transport) Service {
 	return Service{
 		transport:       transport,
-		mappingResolver: NewDependencyMappingResolver(),
+		mappingResolver: internal.NewDependencyMappingResolver(),
 	}
 }