add test suite

internal/instructions/instructions_test.go

@@ -0,0 +1,60 @@
+package instructions
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestFormat_empty(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{"empty_string", "", ""},
+		{"whitespace_only", "   ", ""},
+		{"newline_only", "\n\n", ""},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := Format(tt.input); got != tt.want {
+				t.Errorf("Format(%q) = %q; want %q", tt.input, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestFormat_valid(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+	}{
+		{"single_line", "hello world"},
+		{"multi_line", "line 1\nline 2\nline 3"},
+		{"trailing_newlines", "content\n\n\n"},
+		{"leading_whitespace", "\n\ncontent"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := Format(tt.input)
+			if !strings.HasPrefix(got, "> Instructions:\n") {
+				t.Errorf("missing instructions header")
+			}
+			if !strings.HasSuffix(got, "\n") {
+				t.Errorf("does not end with newline")
+			}
+			lines := strings.Split(got, "\n")
+			for _, line := range lines {
+				if line != "" && !strings.HasPrefix(line, ">") {
+					t.Errorf("line does not start with '>': %q", line)
+				}
+			}
+		})
+	}
+}
+
+func TestFileName_constant(t *testing.T) {
+	if FileName != ".dirmd" {
+		t.Errorf("FileName = %q; want \".dirmd\"", FileName)
+	}
+}