Adding unit tests for EmbedKargsIntoBootImage function

Author: phani0041gs

pkg/isoeditor/kargs_test.go

@@ -2,6 +2,8 @@ package isoeditor
 
 import (
 	"errors"
+	"os"
+	"path/filepath"
 
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
@@ -153,3 +155,139 @@ menuentry 'Fedora CoreOS (Live)' --class fedora --class gnu-linux --class gnu --
 		})
 	})
 })
+
+// Tests for EmbedKargsIntoBootImage
+var _ = Describe("EmbedKargsIntoBootImage", func() {
+	var (
+		baseDir    string // acts as baseIsoPath (where /coreos/kargs.json is read from)
+		stagingDir string // acts as stagingIsoPath (where files are written)
+	)
+
+	writeBaseKargsJSON := func(json string) {
+		p := filepath.Join(baseDir, "coreos", "kargs.json")
+		Expect(os.MkdirAll(filepath.Dir(p), 0755)).To(Succeed())
+		Expect(os.WriteFile(p, []byte(json), 0644)).To(Succeed())
+	}
+
+	// helper to create a target file inside staging dir with a given size (filled with zeros)
+	createStagingFile := func(rel string, size int) string {
+		full := filepath.Join(stagingDir, rel)
+		Expect(os.MkdirAll(filepath.Dir(full), 0755)).To(Succeed())
+		buf := make([]byte, size)
+		Expect(os.WriteFile(full, buf, 0644)).To(Succeed())
+		return full
+	}
+
+	BeforeEach(func() {
+		var err error
+		baseDir, err = os.MkdirTemp("", "iso-base")
+		Expect(err).ToNot(HaveOccurred())
+		stagingDir, err = os.MkdirTemp("", "iso-staging")
+		Expect(err).ToNot(HaveOccurred())
+	})
+
+	AfterEach(func() {
+		os.RemoveAll(baseDir)
+		os.RemoveAll(stagingDir)
+	})
+
+	It("fails when /coreos/kargs.json cannot be read from base ISO path", func() {
+		// Do NOT create base coreos/kargs.json
+		err := EmbedKargsIntoBootImage(baseDir, stagingDir, "any")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("failed to read kargs config"))
+	})
+
+	It("fails when /coreos/kargs.json is malformed", func() {
+		writeBaseKargsJSON(`{ not valid json }`)
+		err := EmbedKargsIntoBootImage(baseDir, stagingDir, "newKargs")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("failed to parse"))
+	})
+
+	It("fails when no kargs file entries are present", func() {
+		writeBaseKargsJSON(`{"default":"abc","files":[],"size":10}`)
+		err := EmbedKargsIntoBootImage(baseDir, stagingDir, "extra")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("no kargs file entries"))
+	})
+
+	It("fails when a listed staging file does not exist", func() {
+		writeBaseKargsJSON(`{
+			"default": "abc",
+			"files": [{"path":"cdboot.img","offset":10}],
+			"size": 100
+		}`)
+		// Don't create cdboot.img in staging
+		err := EmbedKargsIntoBootImage(baseDir, stagingDir, "zzz")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("does not exist"))
+	})
+
+	It("fails when kargs length exceeds configured Size", func() {
+		// default=3 chars, custom=9 chars -> total 12 > size 10
+		writeBaseKargsJSON(`{
+			"default": "abc",
+			"files": [{"path":"cdboot.img","offset":0}],
+			"size": 10
+		}`)
+		_ = createStagingFile("cdboot.img", 32)
+		err := EmbedKargsIntoBootImage(baseDir, stagingDir, "toolonggg")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("exceeds available field size"))
+	})
+
+	It("fails when size is not provided but available space (by file length) is insufficient", func() {
+		// Size=0 means use file size heuristic:
+		// file size 8, offset=4, default len=3 -> append offset = 7, remaining = 1
+		// total needed default+custom = 3 + 3 = 6 > 1 -> error
+		writeBaseKargsJSON(`{
+			"default": "abc",
+			"files": [{"path":"cdboot.img","offset":4}],
+			"size": 0
+		}`)
+		_ = createStagingFile("cdboot.img", 8)
+		err := EmbedKargsIntoBootImage(baseDir, stagingDir, "xyz")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("exceeds available field size"))
+	})
+
+	It("fails when the staging path exists but is a directory (open for write fails)", func() {
+		writeBaseKargsJSON(`{
+			"default": "abc",
+			"files": [{"path":"cdboot.img","offset":5}],
+			"size": 100
+		}`)
+		// Create a directory named cdboot.img
+		Expect(os.MkdirAll(filepath.Join(stagingDir, "cdboot.img"), 0755)).To(Succeed())
+		err := EmbedKargsIntoBootImage(baseDir, stagingDir, "ok")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("failed to open target file"))
+	})
+
+	It("successfully embeds kargs into TWO different files with different offsets", func() {
+		// default is "abc" (len=3)
+		writeBaseKargsJSON(`{
+			"default": "abc",
+			"files": [
+				{"path":"cdboot.img","offset":10},
+				{"path":"coreos/kargs.json","offset":20}
+			],
+			"size": 1024
+		}`)
+		cdboot := createStagingFile("cdboot.img", 256)
+		kargsBin := createStagingFile("coreos/kargs.json", 256)
+
+		custom := "dual-file=ok"
+		Expect(EmbedKargsIntoBootImage(baseDir, stagingDir, custom)).To(Succeed())
+
+		// Verify writes at offset + len(default)
+		cd, err := os.ReadFile(cdboot)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(string(cd[10+3 : 10+3+len(custom)])).To(Equal(custom))
+
+		kb, err := os.ReadFile(kargsBin)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(string(kb[20+3 : 20+3+len(custom)])).To(Equal(custom))
+	})
+})