diff --git a/io/transform/gsheet2csv/cmd/gsheet2env/main_test.go b/io/transform/gsheet2csv/cmd/gsheet2env/main_test.go
new file mode 100644
index 0000000..cc04ab9
--- /dev/null
+++ b/io/transform/gsheet2csv/cmd/gsheet2env/main_test.go
@@ -0,0 +1,213 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"github.com/therootcompany/golib/io/transform/gsheet2csv"
+)
+
+func TestConvert(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		noHeader  bool
+		noExport  bool
+		want      string
+		wantErr   bool
+		errSubstr string
+	}{
+		{
+			name:     "basic 3-column with header",
+			noHeader: false,
+			input: "KEY,VALUE,COMMENT\n" +
+				"FOO,bar,comment here\n" +
+				"BAZ,qux,another comment\n",
+			want: "# comment here\nexport FOO='bar'\n# another comment\nexport BAZ='qux'\n",
+		},
+		{
+			name:     "3-column with --no-header",
+			noHeader: true,
+			input: "KEY,VALUE,COMMENT\n" +
+				"FOO,bar,comment here\n",
+			want: "# COMMENT\nexport KEY='VALUE'\n# comment here\nexport FOO='bar'\n",
+		},
+		{
+			name:     "extra columns ignored",
+			noHeader: false,
+			input: "KEY,VALUE,COMMENT,URL,NOTES\n" +
+				"FOO,bar,comment,https://example.com,extra notes\n",
+			want: "# comment\nexport FOO='bar'\n",
+		},
+		{
+			name:     "2-column no comment",
+			noHeader: false,
+			input: "KEY,VALUE\n" +
+				"FOO,bar\n" +
+				"BAZ,qux\n",
+			want: "export FOO='bar'\nexport BAZ='qux'\n",
+		},
+		{
+			name:     "empty comment column",
+			noHeader: false,
+			input: "KEY,VALUE,COMMENT\n" +
+				"FOO,bar,\n" +
+				"BAZ,qux,has comment\n",
+			want: "export FOO='bar'\n# has comment\nexport BAZ='qux'\n",
+		},
+		{
+			name:     "comment preserved",
+			noHeader: false,
+			input: "# This is a comment\n" +
+				"KEY,VALUE,COMMENT\n" +
+				"FOO,bar,note\n",
+			want: "# This is a comment\n# note\nexport FOO='bar'\n",
+		},
+		{
+			name:     "multi-line comment",
+			noHeader: false,
+			input: "KEY,VALUE,COMMENT\n" +
+				"FOO,bar,\"line1\nline2\"\n",
+			want: "# line1\n# line2\nexport FOO='bar'\n",
+		},
+		{
+			name:     "multi-line value",
+			noHeader: false,
+			input: "KEY,VALUE,COMMENT\n" +
+				"FOO,\"val1\nval2\",note\n",
+			want: "# note\nexport FOO='val1\nval2'\n",
+		},
+		{
+			name:     "single quotes in value escaped",
+			noHeader: false,
+			input: "KEY,VALUE,COMMENT\n" +
+				"FOO,it's value,note\n",
+			want: "# note\nexport FOO='it'\"'\"'s value'\n",
+		},
+		{
+			name:      "invalid key errors",
+			noHeader:  false,
+			input:     "KEY,VALUE,COMMENT\ninvalid-key,val,note\n",
+			wantErr:   true,
+			errSubstr: "invalid key",
+		},
+		{
+			name:     "export prefix optional",
+			noHeader: false,
+			noExport: true,
+			input: "KEY,VALUE,COMMENT\n" +
+				"FOO,bar,note\n",
+			want: "# note\nFOO='bar'\n",
+		},
+		{
+			name:     "empty key produces blank line",
+			noHeader: false,
+			input: "KEY,VALUE,COMMENT\n" +
+				",value,note\n" +
+				"FOO,bar,note\n",
+			want: "\n# note\nexport FOO='bar'\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gsr := gsheet2csv.NewReader(strings.NewReader(tt.input))
+			gsr.Comment = 0
+			gsr.FieldsPerRecord = -1
+
+			var out bytes.Buffer
+			err := convert(gsr, &out, tt.noHeader, tt.noExport)
+
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("expected error containing %q, got nil", tt.errSubstr)
+				} else if !strings.Contains(err.Error(), tt.errSubstr) {
+					t.Errorf("error %q does not contain %q", err.Error(), tt.errSubstr)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Errorf("unexpected error: %v", err)
+				return
+			}
+
+			got := out.String()
+			if got != tt.want {
+				t.Errorf("output mismatch:\ngot:\n%s\nwant:\n%s", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestIsValidKey(t *testing.T) {
+	tests := []struct {
+		key  string
+		want bool
+	}{
+		{"FOO", true},
+		{"FOO_BAR", true},
+		{"FOO123", true},
+		{"A1B2C3", true},
+		{"", true},
+		{"foo", false},
+		{"FOO-BAR", false},
+		{"FOO.BAR", false},
+		{"FOO BAR", false},
+		{"${FOO}", false},
+		{"123ABC", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.key, func(t *testing.T) {
+			got := isValidKey(tt.key)
+			if got != tt.want {
+				t.Errorf("isValidKey(%q) = %v, want %v", tt.key, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestSanitizeComment(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{
+			name:  "simple comment",
+			input: "note",
+			want:  "# note\n",
+		},
+		{
+			name:  "comment with leading/trailing space",
+			input: "  note  ",
+			want:  "# note\n",
+		},
+		{
+			name:  "multi-line comment",
+			input: "line1\nline2",
+			want:  "# line1\n# line2\n",
+		},
+		{
+			name:  "multi-line with CRLF",
+			input: "line1\r\nline2",
+			want:  "# line1\n# line2\n",
+		},
+		{
+			name:  "empty comment",
+			input: "",
+			want:  "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := sanitizeComment(tt.input)
+			if got != tt.want {
+				t.Errorf("sanitizeComment(%q) = %q, want %q", tt.input, got, tt.want)
+			}
+		})
+	}
+}