test: add comprehensive unit test suite (~85 new tests)

Add unit tests across all model and server infrastructure layers,
increasing test count from 7 to 92. Covers serde round-trips, enum
methods, defaults, config parsing, error mapping, PKCE crypto (with
RFC 7636 test vector), OAuth store, and SearXNG ranking/dedup logic.

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

src/infrastructure/searxng.rs

@@ -5,13 +5,13 @@ use dioxus::prelude::*;
 // The #[server] macro generates a client stub for the web build that
 // sends a network request instead of executing this function body.
 #[cfg(feature = "server")]
-mod inner {
+pub(crate) mod inner {
     use serde::Deserialize;
     use std::collections::HashSet;
 
     /// Individual result from the SearXNG search API.
     #[derive(Debug, Deserialize)]
-    pub(super) struct SearxngResult {
+    pub(crate) struct SearxngResult {
         pub title: String,
         pub url: String,
         pub content: Option<String>,
@@ -25,7 +25,7 @@ mod inner {
 
     /// Top-level response from the SearXNG search API.
     #[derive(Debug, Deserialize)]
-    pub(super) struct SearxngResponse {
+    pub(crate) struct SearxngResponse {
         pub results: Vec<SearxngResult>,
     }
 
@@ -40,7 +40,7 @@ mod inner {
     /// # Returns
     ///
     /// The domain host or a fallback "Web" string
-    pub(super) fn extract_source(url_str: &str) -> String {
+    pub(crate) fn extract_source(url_str: &str) -> String {
         url::Url::parse(url_str)
             .ok()
             .and_then(|u| u.host_str().map(String::from))
@@ -64,7 +64,7 @@ mod inner {
     /// # Returns
     ///
     /// Filtered, deduplicated, and ranked results
-    pub(super) fn rank_and_deduplicate(
+    pub(crate) fn rank_and_deduplicate(
         mut results: Vec<SearxngResult>,
         max_results: usize,
     ) -> Vec<SearxngResult> {
@@ -285,3 +285,166 @@ pub async fn get_trending_topics() -> Result<Vec<String>, ServerFnError> {
 
     Ok(topics)
 }
+
+#[cfg(all(test, feature = "server"))]
+mod tests {
+    #![allow(clippy::unwrap_used, clippy::expect_used)]
+
+    use super::inner::*;
+    use pretty_assertions::assert_eq;
+
+    // -----------------------------------------------------------------------
+    // extract_source()
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn extract_source_strips_www() {
+        assert_eq!(
+            extract_source("https://www.example.com/page"),
+            "example.com"
+        );
+    }
+
+    #[test]
+    fn extract_source_returns_domain() {
+        assert_eq!(
+            extract_source("https://techcrunch.com/article"),
+            "techcrunch.com"
+        );
+    }
+
+    #[test]
+    fn extract_source_invalid_url_returns_web() {
+        assert_eq!(extract_source("not-a-url"), "Web");
+    }
+
+    #[test]
+    fn extract_source_no_scheme_returns_web() {
+        // url::Url::parse requires a scheme; bare domain fails
+        assert_eq!(extract_source("example.com/path"), "Web");
+    }
+
+    // -----------------------------------------------------------------------
+    // rank_and_deduplicate()
+    // -----------------------------------------------------------------------
+
+    fn make_result(url: &str, content: &str, score: f64) -> SearxngResult {
+        SearxngResult {
+            title: "Title".into(),
+            url: url.into(),
+            content: if content.is_empty() {
+                None
+            } else {
+                Some(content.into())
+            },
+            published_date: None,
+            thumbnail: None,
+            score,
+        }
+    }
+
+    #[test]
+    fn rank_filters_empty_content() {
+        let results = vec![
+            make_result("https://a.com", "", 10.0),
+            make_result(
+                "https://b.com",
+                "This is meaningful content that passes the length filter",
+                5.0,
+            ),
+        ];
+        let ranked = rank_and_deduplicate(results, 10);
+        assert_eq!(ranked.len(), 1);
+        assert_eq!(ranked[0].url, "https://b.com");
+    }
+
+    #[test]
+    fn rank_filters_short_content() {
+        let results = vec![
+            make_result("https://a.com", "short", 10.0),
+            make_result(
+                "https://b.com",
+                "This content is long enough to pass the 20-char filter threshold",
+                5.0,
+            ),
+        ];
+        let ranked = rank_and_deduplicate(results, 10);
+        assert_eq!(ranked.len(), 1);
+    }
+
+    #[test]
+    fn rank_deduplicates_by_domain_keeps_highest() {
+        let results = vec![
+            make_result(
+                "https://example.com/page1",
+                "First result with enough content here for the filter",
+                3.0,
+            ),
+            make_result(
+                "https://example.com/page2",
+                "Second result with enough content here for the filter",
+                8.0,
+            ),
+        ];
+        let ranked = rank_and_deduplicate(results, 10);
+        assert_eq!(ranked.len(), 1);
+        // Should keep the highest-scored one (page2 with score 8.0)
+        assert_eq!(ranked[0].url, "https://example.com/page2");
+    }
+
+    #[test]
+    fn rank_sorts_by_score_descending() {
+        let results = vec![
+            make_result(
+                "https://a.com/p",
+                "Content A that is long enough to pass the filter check",
+                1.0,
+            ),
+            make_result(
+                "https://b.com/p",
+                "Content B that is long enough to pass the filter check",
+                5.0,
+            ),
+            make_result(
+                "https://c.com/p",
+                "Content C that is long enough to pass the filter check",
+                3.0,
+            ),
+        ];
+        let ranked = rank_and_deduplicate(results, 10);
+        assert_eq!(ranked.len(), 3);
+        assert!(ranked[0].score >= ranked[1].score);
+        assert!(ranked[1].score >= ranked[2].score);
+    }
+
+    #[test]
+    fn rank_truncates_to_max_results() {
+        let results: Vec<_> = (0..20)
+            .map(|i| {
+                make_result(
+                    &format!("https://site{i}.com/page"),
+                    &format!("Content for site {i} that is long enough to pass the filter"),
+                    i as f64,
+                )
+            })
+            .collect();
+        let ranked = rank_and_deduplicate(results, 5);
+        assert_eq!(ranked.len(), 5);
+    }
+
+    #[test]
+    fn rank_empty_input_returns_empty() {
+        let ranked = rank_and_deduplicate(vec![], 10);
+        assert!(ranked.is_empty());
+    }
+
+    #[test]
+    fn rank_all_filtered_returns_empty() {
+        let results = vec![
+            make_result("https://a.com", "", 10.0),
+            make_result("https://b.com", "too short", 5.0),
+        ];
+        let ranked = rank_and_deduplicate(results, 10);
+        assert!(ranked.is_empty());
+    }
+}