Url-regexp: Remove redundant escapes and add test

app/src/test/java/com/termux/app/TermuxActivityTest.java

@@ -0,0 +1,24 @@
+package com.termux.app;
+
+import junit.framework.TestCase;
+
+import java.util.LinkedHashSet;
+
+public class TermuxActivityTest extends TestCase {
+
+    private void assertUrlsAre(String text, String... urls) {
+        LinkedHashSet<String> expected = new LinkedHashSet<>();
+        for (String url : urls) expected.add(url);
+        assertEquals(expected, TermuxActivity.extractUrls(text));
+    }
+
+    public void testExtractUrls() {
+        assertUrlsAre("hello http://example.com world", "http://example.com");
+
+        assertUrlsAre("http://example.com\nhttp://another.com", "http://example.com", "http://another.com");
+
+        assertUrlsAre("hello http://example.com world and http://more.example.com with secure https://more.example.com",
+                "http://example.com", "http://more.example.com", "https://more.example.com");
+    }
+
+}