Initialize Steps with a NewSTEPNAME function [#67]

This seems to be be a more natural separation of concerns--the knowledge
of which config fields map to which parts of a Step belong to the Step,
not to the Plan.

internal/run/depupdate_test.go

@@ -3,6 +3,7 @@ package run
 import (
 	"fmt"
 	"github.com/golang/mock/gomock"
+	"github.com/pelotech/drone-helm3/internal/env"
 	"github.com/stretchr/testify/suite"
 	"strings"
 	"testing"
@@ -31,6 +32,14 @@ func TestDepUpdateTestSuite(t *testing.T) {
 	suite.Run(t, new(DepUpdateTestSuite))
 }
 
+func (suite *DepUpdateTestSuite) TestNewDepUpdate() {
+	cfg := env.Config{
+		Chart: "scatterplot",
+	}
+	d := NewDepUpdate(cfg)
+	suite.Equal("scatterplot", d.Chart)
+}
+
 func (suite *DepUpdateTestSuite) TestPrepareAndExecute() {
 	defer suite.ctrl.Finish()