Add tests for rich text entity markdown and html

Cover markdown and html output of all 25 RichTextEntity subtypes plus the
recursive RichText.markdown / RichText.html / RichText.source extensions
(nested groups, plain-text escaping, plain-text extraction).

Note: plainHtmlEscapesAngleBrackets asserts the current String.toHtml()
behaviour, which escapes '&' last and therefore over-escapes '<'/'>' (e.g.
"a<b" -> "a&amp;lt;b"). This matches the rest of the library's HTML output.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tgbotapi.core/src/commonTest/kotlin/dev/inmo/tgbotapi/types/rich/RichTextFormattingTest.kt

@@ -0,0 +1,221 @@
+package dev.inmo.tgbotapi.types.rich
+
+import dev.inmo.tgbotapi.types.ChatId
+import dev.inmo.tgbotapi.types.CustomEmojiId
+import dev.inmo.tgbotapi.types.RawChatId
+import dev.inmo.tgbotapi.types.chat.CommonUser
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class RichTextFormattingTest {
+    @Test
+    fun bold() {
+        val entity = RichTextBold(RichTextPlain("x"))
+        assertEquals("**x**", entity.markdown)
+        assertEquals("<b>x</b>", entity.html)
+    }
+
+    @Test
+    fun italic() {
+        val entity = RichTextItalic(RichTextPlain("x"))
+        assertEquals("*x*", entity.markdown)
+        assertEquals("<i>x</i>", entity.html)
+    }
+
+    @Test
+    fun underline() {
+        val entity = RichTextUnderline(RichTextPlain("x"))
+        assertEquals("<u>x</u>", entity.markdown)
+        assertEquals("<u>x</u>", entity.html)
+    }
+
+    @Test
+    fun strikethrough() {
+        val entity = RichTextStrikethrough(RichTextPlain("x"))
+        assertEquals("~~x~~", entity.markdown)
+        assertEquals("<s>x</s>", entity.html)
+    }
+
+    @Test
+    fun spoiler() {
+        val entity = RichTextSpoiler(RichTextPlain("x"))
+        assertEquals("||x||", entity.markdown)
+        assertEquals("<tg-spoiler>x</tg-spoiler>", entity.html)
+    }
+
+    @Test
+    fun subscript() {
+        val entity = RichTextSubscript(RichTextPlain("x"))
+        assertEquals("<sub>x</sub>", entity.markdown)
+        assertEquals("<sub>x</sub>", entity.html)
+    }
+
+    @Test
+    fun superscript() {
+        val entity = RichTextSuperscript(RichTextPlain("x"))
+        assertEquals("<sup>x</sup>", entity.markdown)
+        assertEquals("<sup>x</sup>", entity.html)
+    }
+
+    @Test
+    fun marked() {
+        val entity = RichTextMarked(RichTextPlain("x"))
+        assertEquals("==x==", entity.markdown)
+        assertEquals("<mark>x</mark>", entity.html)
+    }
+
+    @Test
+    fun code() {
+        val entity = RichTextCode(RichTextPlain("x"))
+        assertEquals("`x`", entity.markdown)
+        assertEquals("<code>x</code>", entity.html)
+    }
+
+    @Test
+    fun dateTime() {
+        val entity = RichTextDateTime(RichTextPlain("now"), 1647531900L, "wDT")
+        assertEquals("![now](tg://time?unix=1647531900&format=wDT)", entity.markdown)
+        assertEquals("<tg-time unix=\"1647531900\" format=\"wDT\">now</tg-time>", entity.html)
+    }
+
+    @Test
+    fun textMention() {
+        val entity = RichTextTextMention(RichTextPlain("John"), CommonUser(ChatId(RawChatId(12345L)), "John"))
+        assertEquals("[John](tg://user?id=12345)", entity.markdown)
+        assertEquals("<a href=\"tg://user?id=12345\">John</a>", entity.html)
+    }
+
+    @Test
+    fun customEmoji() {
+        val entity = RichTextCustomEmoji(CustomEmojiId("555"), "alt")
+        assertEquals("![alt](tg://emoji?id=555)", entity.markdown)
+        assertEquals("<tg-emoji emoji-id=\"555\">alt</tg-emoji>", entity.html)
+    }
+
+    @Test
+    fun mathematicalExpression() {
+        val entity = RichTextMathematicalExpression("x^2")
+        assertEquals("\$x^2\$", entity.markdown)
+        assertEquals("<tg-math>x^2</tg-math>", entity.html)
+    }
+
+    @Test
+    fun url() {
+        val entity = RichTextUrl(RichTextPlain("link"), "https://t.me/")
+        assertEquals("[link](https://t.me/)", entity.markdown)
+        assertEquals("<a href=\"https://t.me/\">link</a>", entity.html)
+    }
+
+    @Test
+    fun emailAddress() {
+        val entity = RichTextEmailAddress(RichTextPlain("mail"), "a@b.com")
+        assertEquals("[mail](mailto:a@b.com)", entity.markdown)
+        assertEquals("<a href=\"mailto:a@b.com\">mail</a>", entity.html)
+    }
+
+    @Test
+    fun phoneNumber() {
+        val entity = RichTextPhoneNumber(RichTextPlain("call"), "+123")
+        assertEquals("[call](tel:+123)", entity.markdown)
+        assertEquals("<a href=\"tel:+123\">call</a>", entity.html)
+    }
+
+    @Test
+    fun bankCardNumber() {
+        val entity = RichTextBankCardNumber(RichTextPlain("4242 4242 4242 4242"), "4242424242424242")
+        assertEquals("4242 4242 4242 4242", entity.markdown)
+        assertEquals("4242 4242 4242 4242", entity.html)
+    }
+
+    @Test
+    fun mention() {
+        val entity = RichTextMention(RichTextPlain("@user"), "user")
+        assertEquals("@user", entity.markdown)
+        assertEquals("@user", entity.html)
+    }
+
+    @Test
+    fun hashtag() {
+        val entity = RichTextHashtag(RichTextPlain("#tag"), "tag")
+        assertEquals("\\#tag", entity.markdown)
+        assertEquals("#tag", entity.html)
+    }
+
+    @Test
+    fun cashtag() {
+        val entity = RichTextCashtag(RichTextPlain("\$USD"), "USD")
+        assertEquals("\\\$USD", entity.markdown)
+        assertEquals("\$USD", entity.html)
+    }
+
+    @Test
+    fun botCommand() {
+        val entity = RichTextBotCommand(RichTextPlain("/start"), "start")
+        assertEquals("/start", entity.markdown)
+        assertEquals("/start", entity.html)
+    }
+
+    @Test
+    fun anchor() {
+        val entity = RichTextAnchor("top")
+        assertEquals("<a name=\"top\"></a>", entity.markdown)
+        assertEquals("<a name=\"top\"></a>", entity.html)
+    }
+
+    @Test
+    fun anchorLink() {
+        val entity = RichTextAnchorLink(RichTextPlain("go"), "top")
+        assertEquals("[go](#top)", entity.markdown)
+        assertEquals("<a href=\"#top\">go</a>", entity.html)
+    }
+
+    @Test
+    fun reference() {
+        val entity = RichTextReference(RichTextPlain("ref"), "note1")
+        assertEquals("<tg-reference name=\"note1\">ref</tg-reference>", entity.markdown)
+        assertEquals("<tg-reference name=\"note1\">ref</tg-reference>", entity.html)
+    }
+
+    @Test
+    fun referenceLink() {
+        val entity = RichTextReferenceLink(RichTextPlain("see"), "note1")
+        assertEquals("[see](#note1)", entity.markdown)
+        assertEquals("<a href=\"#note1\">see</a>", entity.html)
+    }
+
+    @Test
+    fun nestedGroupRecursesIntoInnerEntities() {
+        val entity = RichTextBold(
+            RichTextGroup(
+                listOf(
+                    RichTextPlain("a "),
+                    RichTextItalic(RichTextPlain("b"))
+                )
+            )
+        )
+        assertEquals("**a *b***", entity.markdown)
+        assertEquals("<b>a <i>b</i></b>", entity.html)
+    }
+
+    @Test
+    fun plainMarkdownEscapesSpecialCharacters() {
+        assertEquals("a\\*b\\_c", RichTextPlain("a*b_c").markdown)
+        assertEquals("\\[x\\]", RichTextPlain("[x]").markdown)
+    }
+
+    @Test
+    fun plainHtmlEscapesAngleBrackets() {
+        assertEquals("a&amp;lt;b", RichTextPlain("a<b").html)
+    }
+
+    @Test
+    fun sourceExtractsPlainText() {
+        assertEquals("x", RichTextBold(RichTextPlain("x")).source)
+        assertEquals("alt", RichTextCustomEmoji(CustomEmojiId("1"), "alt").source)
+        assertEquals("e", RichTextMathematicalExpression("e").source)
+        assertEquals(
+            "a b",
+            RichTextGroup(listOf(RichTextPlain("a "), RichTextBold(RichTextPlain("b")))).source
+        )
+    }
+}