1 files changed, 161 insertions, 0 deletions
diff --git a/pkg/gitdiff/gitdiff_test.go b/pkg/gitdiff/gitdiff_test.go
new file mode 100644
index 0000000..4f63d51
--- /dev/null
+++ b/pkg/gitdiff/gitdiff_test.go
@@ -0,0 +1,161 @@
+package gitdiff
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestTextFragmentValidate(t *testing.T) {
+	tests := map[string]struct {
+		Fragment TextFragment
+		Err      string
+	}{
+		"oldLines": {
+			Fragment: TextFragment{
+				OldPosition:     1,
+				OldLines:        3,
+				NewPosition:     1,
+				NewLines:        2,
+				LeadingContext:  1,
+				TrailingContext: 0,
+				LinesAdded:      1,
+				LinesDeleted:    1,
+				Lines: []Line{
+					{Op: OpContext, Line: "line 1\n"},
+					{Op: OpDelete, Line: "old line 2\n"},
+					{Op: OpAdd, Line: "new line 2\n"},
+				},
+			},
+			Err: "2 old lines",
+		},
+		"newLines": {
+			Fragment: TextFragment{
+				OldPosition:     1,
+				OldLines:        2,
+				NewPosition:     1,
+				NewLines:        3,
+				LeadingContext:  1,
+				TrailingContext: 0,
+				LinesAdded:      1,
+				LinesDeleted:    1,
+				Lines: []Line{
+					{Op: OpContext, Line: "line 1\n"},
+					{Op: OpDelete, Line: "old line 2\n"},
+					{Op: OpAdd, Line: "new line 2\n"},
+				},
+			},
+			Err: "2 new lines",
+		},
+		"leadingContext": {
+			Fragment: TextFragment{
+				OldPosition:     1,
+				OldLines:        2,
+				NewPosition:     1,
+				NewLines:        2,
+				LeadingContext:  0,
+				TrailingContext: 0,
+				LinesAdded:      1,
+				LinesDeleted:    1,
+				Lines: []Line{
+					{Op: OpContext, Line: "line 1\n"},
+					{Op: OpDelete, Line: "old line 2\n"},
+					{Op: OpAdd, Line: "new line 2\n"},
+				},
+			},
+			Err: "1 leading context lines",
+		},
+		"trailingContext": {
+			Fragment: TextFragment{
+				OldPosition:     1,
+				OldLines:        4,
+				NewPosition:     1,
+				NewLines:        3,
+				LeadingContext:  1,
+				TrailingContext: 1,
+				LinesAdded:      1,
+				LinesDeleted:    2,
+				Lines: []Line{
+					{Op: OpContext, Line: "line 1\n"},
+					{Op: OpDelete, Line: "old line 2\n"},
+					{Op: OpAdd, Line: "new line 2\n"},
+					{Op: OpContext, Line: "line 3\n"},
+					{Op: OpDelete, Line: "old line 4\n"},
+				},
+			},
+			Err: "0 trailing context lines",
+		},
+		"linesAdded": {
+			Fragment: TextFragment{
+				OldPosition:     1,
+				OldLines:        4,
+				NewPosition:     1,
+				NewLines:        3,
+				LeadingContext:  1,
+				TrailingContext: 0,
+				LinesAdded:      2,
+				LinesDeleted:    2,
+				Lines: []Line{
+					{Op: OpContext, Line: "line 1\n"},
+					{Op: OpDelete, Line: "old line 2\n"},
+					{Op: OpAdd, Line: "new line 2\n"},
+					{Op: OpContext, Line: "line 3\n"},
+					{Op: OpDelete, Line: "old line 4\n"},
+				},
+			},
+			Err: "1 added lines",
+		},
+		"linesDeleted": {
+			Fragment: TextFragment{
+				OldPosition:     1,
+				OldLines:        4,
+				NewPosition:     1,
+				NewLines:        3,
+				LeadingContext:  1,
+				TrailingContext: 0,
+				LinesAdded:      1,
+				LinesDeleted:    1,
+				Lines: []Line{
+					{Op: OpContext, Line: "line 1\n"},
+					{Op: OpDelete, Line: "old line 2\n"},
+					{Op: OpAdd, Line: "new line 2\n"},
+					{Op: OpContext, Line: "line 3\n"},
+					{Op: OpDelete, Line: "old line 4\n"},
+				},
+			},
+			Err: "2 deleted lines",
+		},
+		"fileCreation": {
+			Fragment: TextFragment{
+				OldPosition:     0,
+				OldLines:        2,
+				NewPosition:     1,
+				NewLines:        1,
+				LeadingContext:  0,
+				TrailingContext: 0,
+				LinesAdded:      1,
+				LinesDeleted:    2,
+				Lines: []Line{
+					{Op: OpDelete, Line: "old line 1\n"},
+					{Op: OpDelete, Line: "old line 2\n"},
+					{Op: OpAdd, Line: "new line\n"},
+				},
+			},
+			Err: "creation fragment",
+		},
+	}
+
+	for name, test := range tests {
+		t.Run(name, func(t *testing.T) {
+			err := test.Fragment.Validate()
+			if test.Err == "" && err != nil {
+				t.Fatalf("unexpected validation error: %v", err)
+			}
+			if test.Err != "" && err == nil {
+				t.Fatal("expected validation error, but got nil")
+			}
+			if !strings.Contains(err.Error(), test.Err) {
+				t.Fatalf("incorrect validation error: %q is not in %q", test.Err, err.Error())
+			}
+		})
+	}
+}