add even more integration tests

commafeed-server/src/test/java/com/commafeed/backend/urlprovider/InPageReferenceFeedURLProviderTest.java

@@ -0,0 +1,91 @@
+package com.commafeed.backend.urlprovider;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class InPageReferenceFeedURLProviderTest {
+
+	private final InPageReferenceFeedURLProvider provider = new InPageReferenceFeedURLProvider();
+
+	@Test
+	void extractsAtomFeedURL() {
+		String url = "http://example.com";
+		String html = """
+				<html>
+					<head>
+						<link type="application/atom+xml" href="/feed.atom">
+					</head>
+					<body>
+					</body>
+				</html>""";
+
+		String result = provider.get(url, html);
+
+		Assertions.assertEquals("http://example.com/feed.atom", result);
+	}
+
+	@Test
+	void extractsRSSFeedURL() {
+		String url = "http://example.com";
+		String html = """
+				<html>
+					<head>
+						<link type="application/rss+xml" href="/feed.rss">
+					</head>
+					<body>
+					</body>
+				</html>""";
+
+		String result = provider.get(url, html);
+
+		Assertions.assertEquals("http://example.com/feed.rss", result);
+	}
+
+	@Test
+	void prefersAtomOverRSS() {
+		String url = "http://example.com";
+		String html = """
+				<html>
+					<head>
+						<link type="application/atom+xml" href="/feed.atom">
+						<link type="application/rss+xml" href="/feed.rss">
+					</head>
+					<body>
+					</body>
+				</html>""";
+
+		String result = provider.get(url, html);
+
+		Assertions.assertEquals("http://example.com/feed.atom", result);
+	}
+
+	@Test
+	void returnsNullForNonHtmlContent() {
+		String url = "http://example.com";
+		String content = """
+				<?xml version="1.0"?>
+					<feed></feed>
+				</xml>""";
+
+		String result = provider.get(url, content);
+
+		Assertions.assertNull(result);
+	}
+
+	@Test
+	void returnsNullForHtmlWithoutFeedLinks() {
+		String url = "http://example.com";
+		String html = """
+				<html>
+					<head>
+						<link type="text/css" href="/style.css">
+					</head>
+					<body>
+					</body>
+				</html>""";
+
+		String result = provider.get(url, html);
+
+		Assertions.assertNull(result);
+	}
+}