1 files changed, 96 insertions, 0 deletions
diff --git a/diff_test.go b/diff_test.go
new file mode 100644
index 0000000..b688294
--- /dev/null
+++ b/diff_test.go
@@ -0,0 +1,96 @@
+package git
+
+import (
+	"errors"
+	"os"
+	"testing"
+)
+
+func TestDiffTreeToTree(t *testing.T) {
+	repo := createTestRepo(t)
+	defer repo.Free()
+	defer os.RemoveAll(repo.Workdir())
+
+	_, originalTreeId := seedTestRepo(t, repo)
+	originalTree, err := repo.LookupTree(originalTreeId)
+
+	checkFatal(t, err)
+
+	_, newTreeId := updateReadme(t, repo, "file changed\n")
+
+	newTree, err := repo.LookupTree(newTreeId)
+	checkFatal(t, err)
+
+	callbackInvoked := false
+	opts := DiffOptions{
+		NotifyCallback: func(diffSoFar *Diff, delta DiffDelta, matchedPathSpec string) error {
+			callbackInvoked = true
+			return nil
+		},
+	}
+
+	diff, err := repo.DiffTreeToTree(originalTree, newTree, &opts)
+	checkFatal(t, err)
+	if !callbackInvoked {
+		t.Fatal("callback not invoked")
+	}
+
+	if diff == nil {
+		t.Fatal("no diff returned")
+	}
+
+	files := make([]string, 0)
+	hunks := make([]DiffHunk, 0)
+	lines := make([]DiffLine, 0)
+	err = diff.ForEach(func(file DiffDelta, progress float64) (DiffForEachHunkCallback, error) {
+		files = append(files, file.OldFile.Path)
+		return func(hunk DiffHunk) (DiffForEachLineCallback, error) {
+			hunks = append(hunks, hunk)
+			return func(line DiffLine) error {
+				lines = append(lines, line)
+				return nil
+			}, nil
+		}, nil
+	}, DiffDetailLines)
+
+	checkFatal(t, err)
+
+	if len(files) != 1 {
+		t.Fatal("Incorrect number of files in diff")
+	}
+
+	if files[0] != "README" {
+		t.Fatal("File in diff was expected to be README")
+	}
+
+	if len(hunks) != 1 {
+		t.Fatal("Incorrect number of hunks in diff")
+	}
+
+	if hunks[0].OldStart != 1 || hunks[0].NewStart != 1 {
+		t.Fatal("Incorrect hunk")
+	}
+
+	if len(lines) != 2 {
+		t.Fatal("Incorrect number of lines in diff")
+	}
+
+	if lines[0].Content != "foo\n" {
+		t.Fatal("Incorrect lines in diff")
+	}
+
+	if lines[1].Content != "file changed\n" {
+		t.Fatal("Incorrect lines in diff")
+	}
+
+	errTest := errors.New("test error")
+
+	err = diff.ForEach(func(file DiffDelta, progress float64) (DiffForEachHunkCallback, error) {
+		return nil, errTest
+	}, DiffDetailLines)
+
+	if err != errTest {
+		t.Fatal("Expected custom error to be returned")
+	}
+
+}