config: improve usage and meaning of validate (#1975)

* discuss miniup config.Default() usage + discourage usage for Default() in comment

* Update internal/config/config_test.go

Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>

* add enterprise version check for config.Default

* split config comment lines

* daniel feedback

* featureset.CanUseEmbeddedMeasurmentsAndImage

---------

Co-authored-by: Daniel Weiße <66256922+daniel-weisse@users.noreply.github.com>

internal/config/config.go

@@ -298,6 +298,7 @@ type AttestationConfig struct {
 }
 
 // Default returns a struct with the default config.
+// IMPORTANT: Ensure that any state mutation is followed by a call to Validate() to ensure that the config is always in a valid state. Avoid usage outside of tests.
 func Default() *Config {
 	return &Config{
 		Version:             Version3,
@@ -367,6 +368,19 @@ func Default() *Config {
 	}
 }
 
+// MiniDefault returns a default config for a mini cluster.
+func MiniDefault() (*Config, error) {
+	config := Default()
+	config.Name = constants.MiniConstellationUID
+	config.RemoveProviderAndAttestationExcept(cloudprovider.QEMU)
+	config.StateDiskSizeGB = 8
+	// only release images (e.g. v2.7.0) use the production NVRAM
+	if !config.IsReleaseImage() {
+		config.Provider.QEMU.NVRAM = "testing"
+	}
+	return config, config.Validate(false)
+}
+
 // fromFile returns config file with `name` read from `fileHandler` by parsing
 // it as YAML. You should prefer config.New to read env vars and validate
 // config in a consistent manner.

internal/config/config_test.go

@@ -376,6 +376,15 @@ func TestValidate(t *testing.T) {
 				return cnf
 			}(),
 		},
+		"miniup default config is not valid because image and measurements are missing in OSS": {
+			cnf: func() *Config {
+				config, _ := MiniDefault()
+				require.NotNil(t, config)
+				return config
+			}(),
+			wantErr:      true,
+			wantErrCount: 2,
+		},
 	}
 
 	for name, tc := range testCases {
@@ -389,7 +398,7 @@ func TestValidate(t *testing.T) {
 				assert.Error(err)
 				var valErr *ValidationError
 				require.ErrorAs(err, &valErr)
-				assert.Equal(tc.wantErrCount, valErr.messagesCount())
+				assert.Equalf(tc.wantErrCount, valErr.messagesCount(), "Got unexpected error count: %d: %s", valErr.messagesCount(), valErr.LongMessage())
 				return
 			}
 			assert.NoError(err)