add tests; fix a couple issues caught by said tests

builder/oracle/classic/config.go

@@ -56,6 +56,10 @@ func NewConfig(raws ...interface{}) (*Config, error) {
 		c.SSHSourceList = "seciplist:/oracle/public/public-internet"
 	}
 
+	if c.Comm.SSHUsername == "" {
+		c.Comm.SSHUsername = "opc"
+	}
+
 	// Validate that all required fields are present
 	var errs *packer.MultiError
 	required := map[string]string{
@@ -76,5 +80,9 @@ func NewConfig(raws ...interface{}) (*Config, error) {
 		errs = packer.MultiErrorAppend(errs, es...)
 	}
 
+	if errs != nil && len(errs.Errors) > 0 {
+		return nil, errs
+	}
+
 	return c, nil
 }

builder/oracle/classic/config_test.go

@@ -0,0 +1,59 @@
+package classic
+
+import (
+	"testing"
+)
+
+func testConfig() map[string]interface{} {
+	return map[string]interface{}{
+		"identity_domain": "abc12345",
+		"username":        "test@hashicorp.com",
+		"password":        "testpassword123",
+		"api_endpoint":    "https://api-test.compute.test.oraclecloud.com/",
+		"image_list":      "/oracle/public/myimage",
+		"shape":           "oc3",
+		"image_name":      "TestImageName",
+		"ssh_username":    "opc",
+	}
+}
+
+func TestConfigAutoFillsSourceList(t *testing.T) {
+	tc := testConfig()
+	conf, err := NewConfig(tc)
+	if err != nil {
+		t.Fatalf("Should not have error: %s", err.Error())
+	}
+	if conf.SSHSourceList != "seciplist:/oracle/public/public-internet" {
+		t.Fatalf("conf.SSHSourceList should have been "+
+			"\"seciplist:/oracle/public/public-internet\" but is \"%s\"",
+			conf.SSHSourceList)
+	}
+}
+
+func TestConfigValidationCatchesMissing(t *testing.T) {
+	required := []string{
+		"username",
+		"password",
+		"api_endpoint",
+		"identity_domain",
+		"image_list",
+		"shape",
+	}
+	for _, key := range required {
+		tc := testConfig()
+		delete(tc, key)
+		_, err := NewConfig(tc)
+		if err == nil {
+			t.Fatalf("Test should have failed when config lacked %s!", key)
+		}
+	}
+}
+
+func TestValidationsIgnoresOptional(t *testing.T) {
+	tc := testConfig()
+	delete(tc, "ssh_username")
+	_, err := NewConfig(tc)
+	if err != nil {
+		t.Fatalf("Test shouldn't care if ssh_username is missing: err: %#v", err.Error())
+	}
+}