Ensure reconcile(p, a, a) == a

tests/idempotence.rs

@@ -0,0 +1,81 @@
+use reconcile_text::{BuiltinTokenizer, Token, reconcile};
+use test_case::{test_case, test_matrix};
+
+#[test_matrix([
+    BuiltinTokenizer::Character,
+    BuiltinTokenizer::Line,
+    BuiltinTokenizer::Markdown,
+    BuiltinTokenizer::Word
+])]
+fn identical_edits_preserve_text(tokenizer: BuiltinTokenizer) {
+    let texts = [
+        "",
+        "a",
+        "b\n",
+        "\r\n\r\n",
+        "# Héllo\n\n- 世界\n",
+        "a a a\nb b b\n",
+    ];
+    for parent in texts {
+        for updated in texts {
+            let input = updated.into();
+            assert_eq!(
+                reconcile(parent, &input, &input, &*tokenizer)
+                    .apply()
+                    .text(),
+                updated,
+                "tokenizer={tokenizer:?}, parent={parent:?}, updated={updated:?}",
+            );
+        }
+    }
+}
+
+#[test_matrix([
+    BuiltinTokenizer::Character,
+    BuiltinTokenizer::Line,
+    BuiltinTokenizer::Markdown,
+    BuiltinTokenizer::Word
+])]
+fn identical_short_edits_preserve_text(tokenizer: BuiltinTokenizer) {
+    let mut texts = vec![String::new()];
+    let mut level = texts.clone();
+    for _ in 0..3 {
+        level = level
+            .iter()
+            .flat_map(|text| ['a', 'b', ' ', '\n'].map(|ch| format!("{text}{ch}")))
+            .collect();
+        texts.extend(level.iter().cloned());
+    }
+
+    for parent in &texts {
+        for updated in &texts {
+            let input = updated.into();
+            assert_eq!(
+                reconcile(parent, &input, &input, &*tokenizer)
+                    .apply()
+                    .text(),
+                *updated,
+                "tokenizer={tokenizer:?}, parent={parent:?}, updated={updated:?}",
+            );
+        }
+    }
+}
+
+#[test_case("A", "a"; "lowercase")]
+#[test_case("a", "A"; "uppercase")]
+#[test_case("Hello WORLD", "HELLO world")]
+#[test_case("X A", "x a\n")]
+#[test_case("A", "new a"; "normalized_suffix")]
+#[test_case("a old B", "A new b"; "normalized_prefix_and_suffix")]
+fn identical_edits_preserve_original_spelling(parent: &str, updated: &str) {
+    let tokenizer = |text: &str| {
+        text.chars()
+            .map(|ch| Token::new(ch.to_ascii_lowercase(), ch.to_string(), false, false))
+            .collect()
+    };
+    let input = updated.into();
+    assert_eq!(
+        reconcile(parent, &input, &input, &tokenizer).apply().text(),
+        updated,
+    );
+}