diff --git a/spatial-index/csv_test.go b/spatial-index/csv_test.go
new file mode 100644
index 00000000..ca71e0db
--- /dev/null
+++ b/spatial-index/csv_test.go
@@ -0,0 +1,124 @@
+package spatialindex
+
+import (
+	"errors"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type testRow struct {
+	A string
+	B string
+}
+
+func fromFuncSimple(data []string, headers []string) (testRow, error) {
+	return testRow{A: data[0], B: data[1]}, nil
+}
+
+func fromFuncWithError(data []string, headers []string) (testRow, error) {
+	return testRow{}, errors.New("parse error")
+}
+
+func TestParseCSV_WithHeader_Success(t *testing.T) {
+	csvData := "a,b\nfoo,bar\nbaz,qux\n"
+	reader := strings.NewReader(csvData)
+
+	var results []Result[testRow]
+	iter := parseCSV(reader, true, fromFuncSimple)
+	for r := range iter {
+		results = append(results, r)
+	}
+
+	require.Len(t, results, 2)
+	require.Equal(t, 1, results[0].LineNum)
+	require.Equal(t, "foo", results[0].Value.A)
+	require.Equal(t, "bar", results[0].Value.B)
+	require.NoError(t, results[0].Error)
+	require.Equal(t, 2, results[1].LineNum)
+	require.Equal(t, "baz", results[1].Value.A)
+	require.Equal(t, "qux", results[1].Value.B)
+	require.NoError(t, results[1].Error)
+}
+
+func TestParseCSV_WithoutHeader_Success(t *testing.T) {
+	csvData := "foo,bar\nbaz,qux\n"
+	reader := strings.NewReader(csvData)
+
+	var results []Result[testRow]
+	iter := parseCSV(reader, false, fromFuncSimple)
+	for r := range iter {
+		results = append(results, r)
+	}
+
+	require.Len(t, results, 2)
+	require.Equal(t, 1, results[0].LineNum)
+	require.Equal(t, "foo", results[0].Value.A)
+	require.Equal(t, "bar", results[0].Value.B)
+	require.NoError(t, results[0].Error)
+	require.Equal(t, 2, results[1].LineNum)
+	require.Equal(t, "baz", results[1].Value.A)
+	require.Equal(t, "qux", results[1].Value.B)
+	require.NoError(t, results[1].Error)
+}
+
+func TestParseCSV_ParseError(t *testing.T) {
+	csvData := "a,b\nfoo,bar\nbaz,qux\n"
+	reader := strings.NewReader(csvData)
+
+	var results []Result[testRow]
+	iter := parseCSV(reader, true, fromFuncWithError)
+	for r := range iter {
+		results = append(results, r)
+	}
+
+	require.Len(t, results, 1)
+	require.Equal(t, 1, results[0].LineNum)
+	require.Error(t, results[0].Error)
+	require.Contains(t, results[0].Error.Error(), "failed to parse CSV line 1")
+}
+
+func TestParseCSV_MalformedLine(t *testing.T) {
+	csvData := "a,b\nfoo\n"
+	reader := strings.NewReader(csvData)
+
+	var results []Result[testRow]
+	iter := parseCSV(reader, true, fromFuncSimple)
+	for r := range iter {
+		results = append(results, r)
+	}
+
+	require.Len(t, results, 1)
+	require.Equal(t, 1, results[0].LineNum)
+	require.Error(t, results[0].Error)
+	// Error message is from underlying csv.Reader
+	require.Contains(t, results[0].Error.Error(), "wrong number of fields")
+}
+
+func TestParseCSV_HeaderReadError(t *testing.T) {
+	// An empty reader will cause an io.EOF when reading headers.
+	reader := strings.NewReader("")
+	iter := parseCSV(reader, true, fromFuncSimple)
+	var results []Result[testRow]
+	for r := range iter {
+		results = append(results, r)
+	}
+	require.Len(t, results, 1)
+	require.Equal(t, 0, results[0].LineNum)
+	require.Error(t, results[0].Error)
+	require.Contains(t, results[0].Error.Error(), "failed to read CSV headers")
+}
+
+func TestParseCSV_YieldStopsEarly(t *testing.T) {
+	csvData := "a,b\nfoo,bar\nbaz,qux\n"
+	reader := strings.NewReader(csvData)
+
+	count := 0
+	iter := parseCSV(reader, true, fromFuncSimple)
+	iter(func(r Result[testRow]) bool {
+		count++
+		return false // stop after first
+	})
+	require.Equal(t, 1, count)
+}