diff --git a/src/xpath/lib b/src/xpath/lib
index 5ec18e4..1e9b871 160000
--- a/src/xpath/lib
+++ b/src/xpath/lib
@@ -1 +1 @@
-Subproject commit 5ec18e4561f754e78d94d0dc6a3c12b020230c64
+Subproject commit 1e9b871bd6b328fa4a130d5b4c0088adc842ed93
diff --git a/tests/xslt/arithmetic.test.ts b/tests/xslt/arithmetic.test.ts
new file mode 100644
index 0000000..b574ab6
--- /dev/null
+++ b/tests/xslt/arithmetic.test.ts
@@ -0,0 +1,133 @@
+import { Xslt, XmlParser } from '../../src/index';
+
+describe('XPath arithmetic operations', () => {
+    let xslt: Xslt;
+    let xmlParser: XmlParser;
+
+    beforeEach(() => {
+        xslt = new Xslt();
+        xmlParser = new XmlParser();
+    });
+
+    it('addition: number + 1 returns 2', async () => {
+        const xml = xmlParser.xmlParse('<page><number>1</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="number + 1"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>2</result>');
+    });
+
+    it('subtraction: number - 1 returns 0', async () => {
+        const xml = xmlParser.xmlParse('<page><number>1</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="number - 1"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>0</result>');
+    });
+
+    it('multiplication: number * 2 returns 2', async () => {
+        const xml = xmlParser.xmlParse('<page><number>1</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="number * 2"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>2</result>');
+    });
+
+    it('division: number div 2 returns 5', async () => {
+        const xml = xmlParser.xmlParse('<page><number>10</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="number div 2"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>5</result>');
+    });
+
+    it('modulo: number mod 3 returns 1', async () => {
+        const xml = xmlParser.xmlParse('<page><number>10</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="number mod 3"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>1</result>');
+    });
+
+    it('node + node: first + second returns correct sum', async () => {
+        const xml = xmlParser.xmlParse('<page><first>3</first><second>4</second></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="first + second"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>7</result>');
+    });
+
+    it('decimal node: price * 2 returns 7', async () => {
+        const xml = xmlParser.xmlParse('<page><price>3.5</price></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="price * 2"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>7</result>');
+    });
+
+    it('attribute node: @value + 1 returns 6', async () => {
+        const xml = xmlParser.xmlParse('<page><item value="5"/></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="item/@value + 1"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>6</result>');
+    });
+
+    it('unary negation on node: -number returns -5', async () => {
+        const xml = xmlParser.xmlParse('<page><number>5</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="-number"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>-5</result>');
+    });
+
+    it('empty node-set in arithmetic does not throw', async () => {
+        // XPath 1.0 typically yields NaN for arithmetic on an empty node-set.
+        // This test only asserts that xsltProcess resolves without throwing.
+        const xml = xmlParser.xmlParse('<page><number>1</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="missing + 1"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        await xslt.xsltProcess(xml, stylesheet);
+    });
+
+    it('plain number select still works: select="number" returns 1', async () => {
+        const xml = xmlParser.xmlParse('<page><number>1</number></page>');
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="page">
+        <result><xsl:value-of select="number"/></result>
+    </xsl:template>
+</xsl:stylesheet>`);
+        const result = await xslt.xsltProcess(xml, stylesheet);
+        expect(result).toBe('<result>1</result>');
+    });
+});
diff --git a/tests/xslt/copy-of.test.tsx b/tests/xslt/copy-of.test.tsx
index 56098cd..5384712 100644
--- a/tests/xslt/copy-of.test.tsx
+++ b/tests/xslt/copy-of.test.tsx
@@ -1,9 +1,48 @@
 import assert from 'assert';
 
-import { XmlParser } from '../../src/dom';
-import { Xslt } from '../../src/xslt';
+import { Xslt, XmlParser } from '../../src/index';
 
 describe('xsl:copy-of', () => {
+    it('keeps comment content stable across repeated identity transforms', async () => {
+        const xslt = new Xslt();
+        const xmlParser = new XmlParser();
+
+        const xmlInput = '<root><!--1234567890 1234567890--></root>';
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="/">
+        <xsl:copy-of select="."/>
+    </xsl:template>
+</xsl:stylesheet>`);
+
+        const firstInputDoc = xmlParser.xmlParse(xmlInput);
+        const firstPass = await xslt.xsltProcess(firstInputDoc, stylesheet);
+        assert.equal(firstPass, xmlInput);
+
+        const secondInputDoc = xmlParser.xmlParse(firstPass);
+        const secondPass = await xslt.xsltProcess(secondInputDoc, stylesheet);
+        assert.equal(secondPass, firstPass);
+    });
+
+    it('keeps empty comments stable across repeated identity transforms', async () => {
+        const xslt = new Xslt();
+        const xmlParser = new XmlParser();
+
+        const xmlInput = '<root><!----></root>';
+        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
+    <xsl:template match="/">
+        <xsl:copy-of select="."/>
+    </xsl:template>
+</xsl:stylesheet>`);
+
+        const firstInputDoc = xmlParser.xmlParse(xmlInput);
+        const firstPass = await xslt.xsltProcess(firstInputDoc, stylesheet);
+        assert.equal(firstPass, xmlInput);
+
+        const secondInputDoc = xmlParser.xmlParse(firstPass);
+        const secondPass = await xslt.xsltProcess(secondInputDoc, stylesheet);
+        assert.equal(secondPass, firstPass);
+    });
+
     it('Trivial', async () => {
         const xmlSource = `<?xml version="1.0" encoding="UTF-8"?>
             <test>
diff --git a/tests/xslt/issue-187.test.ts b/tests/xslt/issue-187.test.ts
deleted file mode 100644
index f95cc46..0000000
--- a/tests/xslt/issue-187.test.ts
+++ /dev/null
@@ -1,43 +0,0 @@
-import { Xslt, XmlParser } from '../../src/index';
-
-describe('Issue #187: Identity transformation adds spaces to comments', () => {
-    it('keeps comment content stable across repeated identity transforms', async () => {
-        const xslt = new Xslt();
-        const xmlParser = new XmlParser();
-
-        const xmlInput = '<root><!--1234567890 1234567890--></root>';
-        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
-    <xsl:template match="/">
-        <xsl:copy-of select="."/>
-    </xsl:template>
-</xsl:stylesheet>`);
-
-        const firstInputDoc = xmlParser.xmlParse(xmlInput);
-        const firstPass = await xslt.xsltProcess(firstInputDoc, stylesheet);
-        expect(firstPass).toBe(xmlInput);
-
-        const secondInputDoc = xmlParser.xmlParse(firstPass);
-        const secondPass = await xslt.xsltProcess(secondInputDoc, stylesheet);
-        expect(secondPass).toBe(firstPass);
-    });
-
-    it('keeps empty comments stable across repeated identity transforms', async () => {
-        const xslt = new Xslt();
-        const xmlParser = new XmlParser();
-
-        const xmlInput = '<root><!----></root>';
-        const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
-    <xsl:template match="/">
-        <xsl:copy-of select="."/>
-    </xsl:template>
-</xsl:stylesheet>`);
-
-        const firstInputDoc = xmlParser.xmlParse(xmlInput);
-        const firstPass = await xslt.xsltProcess(firstInputDoc, stylesheet);
-        expect(firstPass).toBe(xmlInput);
-
-        const secondInputDoc = xmlParser.xmlParse(firstPass);
-        const secondPass = await xslt.xsltProcess(secondInputDoc, stylesheet);
-        expect(secondPass).toBe(firstPass);
-    });
-});
\ No newline at end of file
diff --git a/tests/xslt/issue-183.test.ts b/tests/xslt/template-match.test.ts
similarity index 74%
rename from tests/xslt/issue-183.test.ts
rename to tests/xslt/template-match.test.ts
index 0aea773..5a6c0b1 100644
--- a/tests/xslt/issue-183.test.ts
+++ b/tests/xslt/template-match.test.ts
@@ -1,47 +1,43 @@
 import { Xslt, XmlParser } from '../../src/index';
 
-describe('Issue #183: Template match with nested elements', () => {
-    it('should match //message when nested under <child>', async () => {
-        const xslt = new Xslt();
-        const xmlParser = new XmlParser();
+describe('xsl:template match patterns', () => {
+    let xslt: Xslt;
+    let xmlParser: XmlParser;
 
+    beforeEach(() => {
+        xslt = new Xslt();
+        xmlParser = new XmlParser();
+    });
+
+    it('matches //message when nested under a child element', async () => {
         const xml = xmlParser.xmlParse('<page><child><message>Hello World.</message></child></page>');
         const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
     <xsl:template match="//message">
         <div><xsl:value-of select="."/></div>
     </xsl:template>
 </xsl:stylesheet>`);
-
         const result = await xslt.xsltProcess(xml, stylesheet);
         expect(result).toBe('<div>Hello World.</div>');
     });
 
-    it('should match with explicit path /page/child/message', async () => {
-        const xslt = new Xslt();
-        const xmlParser = new XmlParser();
-
+    it('matches with explicit absolute path /page/child/message', async () => {
         const xml = xmlParser.xmlParse('<page><child><message>Hello World.</message></child></page>');
         const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
     <xsl:template match="/page/child/message">
         <div><xsl:value-of select="."/></div>
     </xsl:template>
 </xsl:stylesheet>`);
-
         const result = await xslt.xsltProcess(xml, stylesheet);
         expect(result).toBe('<div>Hello World.</div>');
     });
 
-    it('should match //message when NOT nested (direct child of root)', async () => {
-        const xslt = new Xslt();
-        const xmlParser = new XmlParser();
-
+    it('matches //message when element is a direct child of root', async () => {
         const xml = xmlParser.xmlParse('<page><message>Hello World.</message></page>');
         const stylesheet = xmlParser.xmlParse(`<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
     <xsl:template match="//message">
         <div><xsl:value-of select="."/></div>
     </xsl:template>
 </xsl:stylesheet>`);
-
         const result = await xslt.xsltProcess(xml, stylesheet);
         expect(result).toBe('<div>Hello World.</div>');
     });