Issue 241 generate also png for dot output (#274)

* code update - when format is dot generating also png file

* new/overridden graphs from running 'make test-update'

* update comment on make test-update

* merge

* adding svg graphs too + warning if dot exec is not found

* warn if graphviz is not installed only

Makefile

@@ -25,6 +25,7 @@ test:
 	@echo -- $@ --
 	go test ./... -v -cover -coverprofile netpolicy.coverprofile
 
-test-update: # overrides/ generates tests' expected output files for relevant tests
+test-update: # overrides/ generates tests' expected output files for relevant tests 
+# if the format is dot - generates also png files
 	@echo -- $@ --
 	go test ./pkg/netpol/connlist/ ./pkg/netpol/diff/ --args --update

pkg/internal/testutils/testutils.go

@@ -4,13 +4,15 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"github.com/np-guard/netpol-analyzer/pkg/internal/output"
+	"github.com/np-guard/netpol-analyzer/pkg/logger"
 )
 
 // a flag for writing/overriding the golden result files for tests
@@ -53,6 +55,11 @@ func CheckActualVsExpectedOutputMatch(t *testing.T, testName, dirName, expectedO
 	if *update {
 		err := output.WriteToFile(actualOutput, expectedOutputFile)
 		require.Nil(t, err, testInfo)
+		// if format is dot - generate/ override also png graph file using graphviz program
+		if strings.HasSuffix(expectedOutputFile, dotSign+output.DOTFormat) {
+			err = generateGraphFilesIfPossible(expectedOutputFile)
+			require.Nil(t, err, testInfo)
+		}
 		return
 	}
 	// read expected output file
@@ -80,3 +87,28 @@ func CheckErrorContainment(t *testing.T, testInfo, expectedErrorMsg, actualErrMs
 	require.Contains(t, actualErrMsg, expectedErrorMsg, "err/warn message mismatch for test: %q, actual: %q, expected contains: %q",
 		testInfo, actualErrMsg, expectedErrorMsg)
 }
+
+const (
+	// the executable we need from graphviz is "dot"
+	executableNameForGraphviz = output.DOTFormat
+	dotSign                   = "."
+)
+
+var graphsSuffixes = []string{"png", "svg"}
+
+// checks if "graphviz" executable exists, if yes runs a cmd to generates a png graph file from the dot output
+func generateGraphFilesIfPossible(dotFilePath string) error {
+	// check if graphviz is installed to continue
+	if _, err := exec.LookPath(executableNameForGraphviz); err != nil {
+		logger.NewDefaultLogger().Warnf("dot executable of graphviz was not found. Output Graphs will not be generated")
+		return nil
+	}
+	for _, graphSuffix := range graphsSuffixes {
+		graphFilePath := dotFilePath + dotSign + graphSuffix
+		cmd := exec.Command("dot", dotFilePath, "-T"+graphSuffix, "-o", graphFilePath) //nolint:gosec // nosec
+		if err := cmd.Run(); err != nil {
+			return err
+		}
+	}
+	return nil
+}