test: add mock-based site extractor test infrastructure

Create exported extractortest package with MockBrowser, MockDocument,
and MockNode that support selector-based responses for testing site
extractors without a real browser.

Add extraction tests for DuckDuckGo (result parsing, empty results, no
links, full search flow) and Powerball (drawing parsing, next drawing
parsing with billion/million, error cases, full GetCurrent flow).

Closes #21
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sites/duckduckgo/extract_test.go

@@ -0,0 +1,137 @@
+package duckduckgo
+
+import (
+	"context"
+	"testing"
+
+	"gitea.stevedudenhoeffer.com/steve/go-extractor"
+	"gitea.stevedudenhoeffer.com/steve/go-extractor/extractortest"
+)
+
+func makeResultNode(url, title, desc string) *extractortest.MockNode {
+	return &extractortest.MockNode{
+		Children: map[string]extractor.Nodes{
+			`a[href][target="_self"]`: {
+				&extractortest.MockNode{Attrs: map[string]string{"href": url}},
+			},
+			"h2": {
+				&extractortest.MockNode{TextValue: title},
+			},
+			"span > span": {
+				&extractortest.MockNode{TextValue: desc},
+			},
+		},
+	}
+}
+
+func TestExtractResults(t *testing.T) {
+	doc := &extractortest.MockDocument{
+		URLValue: "https://duckduckgo.com/?q=test",
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{
+				`article[id^="r1-"]`: {
+					makeResultNode("https://example.com", "Example", "An example site"),
+					makeResultNode("https://golang.org", "Go", "Go programming language"),
+				},
+			},
+		},
+	}
+
+	results, err := extractResults(doc)
+	if err != nil {
+		t.Fatalf("extractResults() error: %v", err)
+	}
+
+	if len(results) != 2 {
+		t.Fatalf("expected 2 results, got %d", len(results))
+	}
+
+	if results[0].URL != "https://example.com" {
+		t.Errorf("results[0].URL = %q, want %q", results[0].URL, "https://example.com")
+	}
+	if results[0].Title != "Example" {
+		t.Errorf("results[0].Title = %q, want %q", results[0].Title, "Example")
+	}
+	if results[0].Description != "An example site" {
+		t.Errorf("results[0].Description = %q, want %q", results[0].Description, "An example site")
+	}
+
+	if results[1].URL != "https://golang.org" {
+		t.Errorf("results[1].URL = %q, want %q", results[1].URL, "https://golang.org")
+	}
+	if results[1].Title != "Go" {
+		t.Errorf("results[1].Title = %q, want %q", results[1].Title, "Go")
+	}
+}
+
+func TestExtractResults_NoResults(t *testing.T) {
+	doc := &extractortest.MockDocument{
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{
+				`article[id^="r1-"]`: {},
+			},
+		},
+	}
+
+	results, err := extractResults(doc)
+	if err != nil {
+		t.Fatalf("extractResults() error: %v", err)
+	}
+	if len(results) != 0 {
+		t.Errorf("expected 0 results, got %d", len(results))
+	}
+}
+
+func TestExtractResults_NoLinks(t *testing.T) {
+	doc := &extractortest.MockDocument{
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{
+				`article[id^="r1-"]`: {
+					&extractortest.MockNode{
+						Children: map[string]extractor.Nodes{
+							`a[href][target="_self"]`: {},
+						},
+					},
+				},
+			},
+		},
+	}
+
+	results, err := extractResults(doc)
+	if err != nil {
+		t.Fatalf("extractResults() error: %v", err)
+	}
+	if len(results) != 0 {
+		t.Errorf("expected 0 results (no links), got %d", len(results))
+	}
+}
+
+func TestSearch_UsesMockBrowser(t *testing.T) {
+	doc := &extractortest.MockDocument{
+		URLValue: "https://duckduckgo.com/?q=test",
+		MockNode: extractortest.MockNode{
+			Children: map[string]extractor.Nodes{
+				`article[id^="r1-"]`: {
+					makeResultNode("https://example.com", "Example", "Example description"),
+				},
+			},
+		},
+	}
+
+	browser := &extractortest.MockBrowser{
+		Documents: map[string]*extractortest.MockDocument{
+			"https://duckduckgo.com/?kp=-2&q=test": doc,
+		},
+	}
+
+	results, err := DefaultConfig.Search(context.Background(), browser, "test")
+	if err != nil {
+		t.Fatalf("Search() error: %v", err)
+	}
+	if len(results) != 1 {
+		t.Fatalf("expected 1 result, got %d", len(results))
+	}
+	if results[0].URL != "https://example.com" {
+		t.Errorf("results[0].URL = %q, want %q", results[0].URL, "https://example.com")
+	}
+}