1 files changed, 93 insertions, 0 deletions
diff --git a/app/src/test/java/org/terst/feedreader/data/FeedDiscoveryTest.kt b/app/src/test/java/org/terst/feedreader/data/FeedDiscoveryTest.kt
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+++ b/app/src/test/java/org/terst/feedreader/data/FeedDiscoveryTest.kt
@@ -0,0 +1,93 @@
+package org.terst.feedreader.data
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Test
+
+/**
+ * Finding the feed when what you were given is a site.
+ *
+ * Reported live: "Can't subscribe to https://heathercoxrichardson.substack.com/". Pasting a
+ * site's home page was the only thing to hand -- a site does not advertise its feed URL
+ * anywhere a reader can see, it advertises it in a <link rel="alternate"> that every other
+ * reader looks for and this one did not.
+ */
+class FeedDiscoveryTest {
+
+    /** Verbatim from the reported page, 2026-10-21. */
+    private val substackHead =
+        """<!doctype html><html><head><title>Letters from an American</title>""" +
+            """<link rel="alternate" type="application/rss+xml" href="/feed" """ +
+            """title="Letters from an American"/></head><body>...</body></html>"""
+
+    @Test
+    fun `finds the feed a Substack home page advertises, resolved against the site`() {
+        assertEquals(
+            "https://heathercoxrichardson.substack.com/feed",
+            FeedDiscovery.findFeedUrl(substackHead, "https://heathercoxrichardson.substack.com/")
+        )
+    }
+
+    @Test
+    fun `finds an Atom feed too`() {
+        val html = """<link rel="alternate" type="application/atom+xml" href="/atom.xml">"""
+
+        assertEquals("https://example.com/atom.xml", FeedDiscovery.findFeedUrl(html, "https://example.com/"))
+    }
+
+    @Test
+    fun `keeps an absolute href as it stands`() {
+        val html = """<link rel="alternate" type="application/rss+xml" href="https://feeds.example.net/x.xml">"""
+
+        assertEquals("https://feeds.example.net/x.xml", FeedDiscovery.findFeedUrl(html, "https://example.com/blog/"))
+    }
+
+    @Test
+    fun `resolves a relative href against the page, not the site root`() {
+        val html = """<link rel="alternate" type="application/rss+xml" href="feed.xml">"""
+
+        assertEquals("https://example.com/blog/feed.xml", FeedDiscovery.findFeedUrl(html, "https://example.com/blog/"))
+    }
+
+    @Test
+    fun `copes with the attributes in any order and single quotes`() {
+        val html = """<link type='application/rss+xml' href='/rss' rel='alternate'>"""
+
+        assertEquals("https://example.com/rss", FeedDiscovery.findFeedUrl(html, "https://example.com"))
+    }
+
+    @Test
+    fun `prefers the first feed when a page advertises several`() {
+        val html =
+            """<link rel="alternate" type="application/rss+xml" href="/feed" title="Posts">""" +
+                """<link rel="alternate" type="application/rss+xml" href="/comments/feed" title="Comments">"""
+
+        assertEquals("https://example.com/feed", FeedDiscovery.findFeedUrl(html, "https://example.com/"))
+    }
+
+    @Test
+    fun `ignores an alternate link that is not a feed`() {
+        val html =
+            """<link rel="alternate" hreflang="fr" href="/fr/">""" +
+                """<link rel="alternate" type="application/json" href="/feed.json">"""
+
+        assertNull(FeedDiscovery.findFeedUrl(html, "https://example.com/"))
+    }
+
+    @Test
+    fun `a page with no feed at all reports nothing rather than guessing a path`() {
+        assertNull(FeedDiscovery.findFeedUrl("<html><head></head><body>hi</body></html>", "https://example.com/"))
+    }
+
+    @Test
+    fun `an http feed link is upgraded, since the app cannot fetch cleartext`() {
+        val html = """<link rel="alternate" type="application/rss+xml" href="http://example.com/feed">"""
+
+        assertEquals("https://example.com/feed", FeedDiscovery.findFeedUrl(html, "https://example.com/"))
+    }
+
+    @Test
+    fun `xml declaration means this was already a feed, so there is nothing to discover`() {
+        assertNull(FeedDiscovery.findFeedUrl("<?xml version=\"1.0\"?><rss><channel></channel></rss>", "https://x/f"))
+    }
+}