1 files changed, 46 insertions, 0 deletions
diff --git a/app/src/test/java/org/terst/feedreader/ui/ReaderMathTest.kt b/app/src/test/java/org/terst/feedreader/ui/ReaderMathTest.kt
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+++ b/app/src/test/java/org/terst/feedreader/ui/ReaderMathTest.kt
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+package org.terst.feedreader.ui
+
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * The reader's end of maths rendering.
+ *
+ * Extraction converts a page's TeX source to MathML (see ReaderExtractor), which the
+ * WebView renders natively -- no script, no webfont, no stylesheet of KaTeX's. Two things
+ * still have to be true of the reader HTML itself: the MathML has to reach the WebView
+ * intact (the wrapping passes rewrite iframes and images, and must not touch it), and a
+ * wide equation must not be able to drag the whole article into horizontal scrolling --
+ * an aligned multi-line derivation is routinely wider than a phone screen, and `math`
+ * does not obey the `img`/`svg` clamps already in the stylesheet.
+ */
+class ReaderMathTest {
+
+    private val displayMath =
+        "<math xmlns=\"http://www.w3.org/1998/Math/MathML\" display=\"block\"><semantics>" +
+            "<mtable><mtr><mtd><mi>t</mi></mtd></mtr></mtable></semantics></math>"
+
+    @Test
+    fun `mathml reaches the webview unchanged`() {
+        val html = wrapReaderHtml("<p>A slice of the set:</p>$displayMath<p>and so on.</p>")
+        assertTrue("MathML must survive the reader's HTML assembly verbatim", html.contains(displayMath))
+    }
+
+    @Test
+    fun `a wide equation scrolls inside itself instead of scrolling the article`() {
+        val html = wrapReaderHtml("<p>x</p>$displayMath")
+        val style = html.substringAfter("<style>").substringBefore("</style>")
+        val displayMathRule = style.lines()
+            .joinToString(" ")
+            .substringAfter("math[display=\"block\"]", "")
+            .substringBefore("}")
+        assertTrue(
+            "the stylesheet needs a math[display=\"block\"] rule, found none in:\n$style",
+            displayMathRule.isNotBlank()
+        )
+        assertTrue(
+            "display maths must scroll within its own box, got: $displayMathRule",
+            displayMathRule.contains("overflow-x: auto")
+        )
+    }
+}