Add first failing test for the flattener

Signed-off-by: Domenico Luciani <[email protected]>

pkg/buildpack/flattener.go

@@ -0,0 +1,16 @@
+package buildpack
+
+type Flattener interface {
+	FlatBuildpacks()
+}
+
+type BuildpacksFlattener struct {
+}
+
+func NewBuildpacksFlattener() BuildpacksFlattener {
+	return BuildpacksFlattener{}
+}
+
+func (bp BuildpacksFlattener) FlatBuildpacks(bps []BuildModule) []BuildModule {
+	return bps //TODO: Implementation
+}

pkg/buildpack/flattener_test.go

@@ -0,0 +1,70 @@
+package buildpack_test
+
+import (
+	"testing"
+
+	"github.com/buildpacks/lifecycle/api"
+	"github.com/sclevine/spec"
+	"github.com/sclevine/spec/report"
+
+	ifakes "github.com/buildpacks/pack/internal/fakes"
+	"github.com/buildpacks/pack/pkg/buildpack"
+	"github.com/buildpacks/pack/pkg/dist"
+	h "github.com/buildpacks/pack/testhelpers"
+)
+
+func TestFlattener(t *testing.T) {
+	spec.Run(t, "Flattener", testFlattener, spec.Report(report.Terminal{}))
+}
+
+func testFlattener(t *testing.T, when spec.G, it spec.S) {
+	var (
+		bp1 buildpack.BuildModule
+		bp2 buildpack.BuildModule
+		bp3 buildpack.BuildModule
+		err error
+	)
+
+	it.Before(func() {
+		bp1, err = ifakes.NewFakeBuildpack(dist.BuildpackDescriptor{
+			WithAPI: api.MustParse("0.2"),
+			WithInfo: dist.ModuleInfo{
+				ID:      "buildpack-1-id",
+				Version: "buildpack-1-version",
+			},
+		}, 0644)
+		h.AssertNil(t, err)
+
+		bp2, err = ifakes.NewFakeBuildpack(dist.BuildpackDescriptor{
+			WithAPI: api.MustParse("0.2"),
+			WithInfo: dist.ModuleInfo{
+				ID:      "buildpack-2-id",
+				Version: "buildpack-2-version",
+			},
+		}, 0644)
+		h.AssertNil(t, err)
+
+		bp3, err = ifakes.NewFakeBuildpack(dist.BuildpackDescriptor{
+			WithAPI: api.MustParse("0.2"),
+			WithInfo: dist.ModuleInfo{
+				ID:      "buildpack-3-id",
+				Version: "buildpack-3-version",
+			},
+		}, 0644)
+		h.AssertNil(t, err)
+	})
+
+	when("Flattener has been called", func() {
+		var (
+			flattener buildpack.BuildpacksFlattener
+		)
+		it.Before(func() {
+			flattener = buildpack.NewBuildpacksFlattener()
+		})
+
+		it("flats the buildpacks that has been passed", func() {
+			bps := flattener.FlatBuildpacks([]buildpack.BuildModule{bp1, bp2, bp3})
+			h.AssertEq(t, len(bps), 1)
+		})
+	})
+}