diff --git a/docs/config/setup/modules/mermaidAPI.md b/docs/config/setup/modules/mermaidAPI.md
index 591b6841a0..72f18cace9 100644
--- a/docs/config/setup/modules/mermaidAPI.md
+++ b/docs/config/setup/modules/mermaidAPI.md
@@ -96,7 +96,7 @@ mermaid.initialize(config);
 
 #### Defined in
 
-[mermaidAPI.ts:663](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/mermaidAPI.ts#L663)
+[mermaidAPI.ts:667](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/mermaidAPI.ts#L667)
 
 ## Functions
 
diff --git a/packages/mermaid/src/accessibility.spec.ts b/packages/mermaid/src/accessibility.spec.ts
index 7a3ab7f105..7745e02ef8 100644
--- a/packages/mermaid/src/accessibility.spec.ts
+++ b/packages/mermaid/src/accessibility.spec.ts
@@ -1,27 +1,24 @@
 import { MockedD3 } from './tests/MockedD3.js';
 import { setA11yDiagramInfo, addSVGa11yTitleDescription } from './accessibility.js';
-import { D3Element } from './mermaidAPI.js';
+import type { D3Element } from './mermaidAPI.js';
 
 describe('accessibility', () => {
-  const fauxSvgNode = new MockedD3();
+  const fauxSvgNode: MockedD3 = new MockedD3();
 
   describe('setA11yDiagramInfo', () => {
-    it('sets the svg element role to "graphics-document document"', () => {
-      // @ts-ignore  Required to easily handle the d3 select types
+    it('should set svg element role to "graphics-document document"', () => {
       const svgAttrSpy = vi.spyOn(fauxSvgNode, 'attr').mockReturnValue(fauxSvgNode);
       setA11yDiagramInfo(fauxSvgNode, 'flowchart');
       expect(svgAttrSpy).toHaveBeenCalledWith('role', 'graphics-document document');
     });
 
-    it('sets the aria-roledescription to the diagram type', () => {
-      // @ts-ignore  Required to easily handle the d3 select types
+    it('should set aria-roledescription to the diagram type', () => {
       const svgAttrSpy = vi.spyOn(fauxSvgNode, 'attr').mockReturnValue(fauxSvgNode);
       setA11yDiagramInfo(fauxSvgNode, 'flowchart');
       expect(svgAttrSpy).toHaveBeenCalledWith('aria-roledescription', 'flowchart');
     });
 
-    it('does not set the aria-roledescription if the diagram type is empty', () => {
-      // @ts-ignore  Required to easily handle the d3 select types
+    it('should not set aria-roledescription if the diagram type is empty', () => {
       const svgAttrSpy = vi.spyOn(fauxSvgNode, 'attr').mockReturnValue(fauxSvgNode);
       setA11yDiagramInfo(fauxSvgNode, '');
       expect(svgAttrSpy).toHaveBeenCalledTimes(1);
@@ -32,8 +29,8 @@ describe('accessibility', () => {
   describe('addSVGa11yTitleDescription', () => {
     const givenId = 'theBaseId';
 
-    describe('with the given svg d3 object:', () => {
-      it('does nothing if there is no insert defined', () => {
+    describe('with svg d3 object', () => {
+      it('should do nothing if there is no insert defined', () => {
         const noInsertSvg = {
           attr: vi.fn(),
         };
@@ -42,26 +39,25 @@ describe('accessibility', () => {
         expect(noInsertAttrSpy).not.toHaveBeenCalled();
       });
 
-      // ----------------
-      // Convenience functions to DRY up the spec
+      // convenience functions to DRY up the spec
 
-      function expectAriaLabelledByIsTitleId(
+      function expectAriaLabelledByItTitleId(
         svgD3Node: D3Element,
-        title: string | null | undefined,
-        desc: string | null | undefined,
+        title: string | undefined,
+        desc: string | undefined,
         givenId: string
-      ) {
+      ): void {
         const svgAttrSpy = vi.spyOn(svgD3Node, 'attr').mockReturnValue(svgD3Node);
         addSVGa11yTitleDescription(svgD3Node, title, desc, givenId);
         expect(svgAttrSpy).toHaveBeenCalledWith('aria-labelledby', `chart-title-${givenId}`);
       }
 
-      function expectAriaDescribedByIsDescId(
+      function expectAriaDescribedByItDescId(
         svgD3Node: D3Element,
-        title: string | null | undefined,
-        desc: string | null | undefined,
+        title: string | undefined,
+        desc: string | undefined,
         givenId: string
-      ) {
+      ): void {
         const svgAttrSpy = vi.spyOn(svgD3Node, 'attr').mockReturnValue(svgD3Node);
         addSVGa11yTitleDescription(svgD3Node, title, desc, givenId);
         expect(svgAttrSpy).toHaveBeenCalledWith('aria-describedby', `chart-desc-${givenId}`);
@@ -69,154 +65,148 @@ describe('accessibility', () => {
 
       function a11yTitleTagInserted(
         svgD3Node: D3Element,
-        title: string | null | undefined,
-        desc: string | null | undefined,
+        title: string | undefined,
+        desc: string | undefined,
         givenId: string,
         callNumber: number
-      ) {
+      ): void {
         a11yTagInserted(svgD3Node, title, desc, givenId, callNumber, 'title', title);
       }
 
       function a11yDescTagInserted(
         svgD3Node: D3Element,
-        title: string | null | undefined,
-        desc: string | null | undefined,
+        title: string | undefined,
+        desc: string | undefined,
         givenId: string,
         callNumber: number
-      ) {
+      ): void {
         a11yTagInserted(svgD3Node, title, desc, givenId, callNumber, 'desc', desc);
       }
 
       function a11yTagInserted(
-        svgD3Node: D3Element,
-        title: string | null | undefined,
-        desc: string | null | undefined,
+        _svgD3Node: D3Element,
+        title: string | undefined,
+        desc: string | undefined,
         givenId: string,
         callNumber: number,
         expectedPrefix: string,
-        expectedText: string | null | undefined
-      ) {
-        const fauxInsertedD3 = new MockedD3();
-        const svgInsertSpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxInsertedD3);
-        // @ts-ignore  Required to easily handle the d3 select types
+        expectedText: string | undefined
+      ): void {
+        const fauxInsertedD3: MockedD3 = new MockedD3();
+        const svginsertpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxInsertedD3);
         const titleAttrSpy = vi.spyOn(fauxInsertedD3, 'attr').mockReturnValue(fauxInsertedD3);
         const titleTextSpy = vi.spyOn(fauxInsertedD3, 'text');
 
         addSVGa11yTitleDescription(fauxSvgNode, title, desc, givenId);
-        expect(svgInsertSpy).toHaveBeenCalledWith(expectedPrefix, ':first-child');
+        expect(svginsertpy).toHaveBeenCalledWith(expectedPrefix, ':first-child');
         expect(titleAttrSpy).toHaveBeenCalledWith('id', `chart-${expectedPrefix}-${givenId}`);
         expect(titleTextSpy).toHaveBeenNthCalledWith(callNumber, expectedText);
       }
-      // ----------------
 
-      describe('given an a11y title', () => {
+      describe('with a11y title', () => {
         const a11yTitle = 'a11y title';
 
-        describe('given an a11y description', () => {
+        describe('with a11y description', () => {
           const a11yDesc = 'a11y description';
 
-          it('sets aria-labelledby to the title id inserted as a child', () => {
-            expectAriaLabelledByIsTitleId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
+          it('shold set aria-labelledby to the title id inserted as a child', () => {
+            expectAriaLabelledByItTitleId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
           });
 
-          it('sets aria-describedby to the description id inserted as a child', () => {
-            expectAriaDescribedByIsDescId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
+          it('should set aria-describedby to the description id inserted as a child', () => {
+            expectAriaDescribedByItDescId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
           });
 
-          it('inserts a title tag as the first child with the text set to the accTitle given', () => {
+          it('should insert title tag as the first child with the text set to the accTitle given', () => {
             a11yTitleTagInserted(fauxSvgNode, a11yTitle, a11yDesc, givenId, 2);
           });
 
-          it('inserts a desc tag as the 2nd child with the text set to accDescription given', () => {
+          it('should insert desc tag as the 2nd child with the text set to accDescription given', () => {
             a11yDescTagInserted(fauxSvgNode, a11yTitle, a11yDesc, givenId, 1);
           });
         });
 
-        describe(`no a11y description`, () => {
+        describe(`without a11y description`, () => {
           const a11yDesc = undefined;
 
-          it('sets aria-labelledby to the title id inserted as a child', () => {
-            expectAriaLabelledByIsTitleId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
+          it('should set aria-labelledby to the title id inserted as a child', () => {
+            expectAriaLabelledByItTitleId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
           });
 
-          it('no aria-describedby is set', () => {
-            // @ts-ignore Required to easily handle the d3 select types
+          it('should not set aria-describedby', () => {
             const svgAttrSpy = vi.spyOn(fauxSvgNode, 'attr').mockReturnValue(fauxSvgNode);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
             expect(svgAttrSpy).not.toHaveBeenCalledWith('aria-describedby', expect.anything());
           });
 
-          it('inserts a title tag as the first child with the text set to the accTitle given', () => {
+          it('should insert title tag as the first child with the text set to the accTitle given', () => {
             a11yTitleTagInserted(fauxSvgNode, a11yTitle, a11yDesc, givenId, 1);
           });
 
-          it('no description tag is inserted', () => {
-            const fauxTitle = new MockedD3();
-            const svgInsertSpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxTitle);
+          it('should not insert description tag', () => {
+            const fauxTitle: MockedD3 = new MockedD3();
+            const svginsertpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxTitle);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
-            expect(svgInsertSpy).not.toHaveBeenCalledWith('desc', ':first-child');
+            expect(svginsertpy).not.toHaveBeenCalledWith('desc', ':first-child');
           });
         });
       });
 
-      describe('no a11y title', () => {
+      describe('without a11y title', () => {
         const a11yTitle = undefined;
 
-        describe('given an a11y description', () => {
+        describe('with a11y description', () => {
           const a11yDesc = 'a11y description';
 
-          it('no aria-labelledby is set', () => {
-            // @ts-ignore Required to easily handle the d3 select types
+          it('should not set aria-labelledby', () => {
             const svgAttrSpy = vi.spyOn(fauxSvgNode, 'attr').mockReturnValue(fauxSvgNode);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
             expect(svgAttrSpy).not.toHaveBeenCalledWith('aria-labelledby', expect.anything());
           });
 
-          it('no title tag inserted', () => {
-            const fauxTitle = new MockedD3();
-            const svgInsertSpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxTitle);
+          it('should not insert title tag', () => {
+            const fauxTitle: MockedD3 = new MockedD3();
+            const svginsertpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxTitle);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
-            expect(svgInsertSpy).not.toHaveBeenCalledWith('title', ':first-child');
+            expect(svginsertpy).not.toHaveBeenCalledWith('title', ':first-child');
           });
 
-          it('sets aria-describedby to the description id inserted as a child', () => {
-            expectAriaDescribedByIsDescId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
+          it('should set aria-describedby to the description id inserted as a child', () => {
+            expectAriaDescribedByItDescId(fauxSvgNode, a11yTitle, a11yDesc, givenId);
           });
 
-          it('inserts a desc tag as the 2nd child with the text set to accDescription given', () => {
+          it('should insert desc tag as the 2nd child with the text set to accDescription given', () => {
             a11yDescTagInserted(fauxSvgNode, a11yTitle, a11yDesc, givenId, 1);
           });
         });
 
-        describe('no a11y description', () => {
+        describe('without a11y description', () => {
           const a11yDesc = undefined;
 
-          it('no aria-labelledby is set', () => {
-            // @ts-ignore Required to easily handle the d3 select types
+          it('should not set aria-labelledby', () => {
             const svgAttrSpy = vi.spyOn(fauxSvgNode, 'attr').mockReturnValue(fauxSvgNode);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
             expect(svgAttrSpy).not.toHaveBeenCalledWith('aria-labelledby', expect.anything());
           });
 
-          it('no aria-describedby is set', () => {
-            // @ts-ignore Required to easily handle the d3 select types
+          it('should not set aria-describedby', () => {
             const svgAttrSpy = vi.spyOn(fauxSvgNode, 'attr').mockReturnValue(fauxSvgNode);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
             expect(svgAttrSpy).not.toHaveBeenCalledWith('aria-describedby', expect.anything());
           });
 
-          it('no title tag inserted', () => {
-            const fauxTitle = new MockedD3();
-            const svgInsertSpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxTitle);
+          it('should not insert title tag', () => {
+            const fauxTitle: MockedD3 = new MockedD3();
+            const svginsertpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxTitle);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
-            expect(svgInsertSpy).not.toHaveBeenCalledWith('title', ':first-child');
+            expect(svginsertpy).not.toHaveBeenCalledWith('title', ':first-child');
           });
 
-          it('no description tag inserted', () => {
-            const fauxDesc = new MockedD3();
-            const svgInsertSpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxDesc);
+          it('should not insert  description tag', () => {
+            const fauxDesc: MockedD3 = new MockedD3();
+            const svginsertpy = vi.spyOn(fauxSvgNode, 'insert').mockReturnValue(fauxDesc);
             addSVGa11yTitleDescription(fauxSvgNode, a11yTitle, a11yDesc, givenId);
-            expect(svgInsertSpy).not.toHaveBeenCalledWith('desc', ':first-child');
+            expect(svginsertpy).not.toHaveBeenCalledWith('desc', ':first-child');
           });
         });
       });
diff --git a/packages/mermaid/src/accessibility.ts b/packages/mermaid/src/accessibility.ts
index eba3ba9a75..69e22b3011 100644
--- a/packages/mermaid/src/accessibility.ts
+++ b/packages/mermaid/src/accessibility.ts
@@ -1,13 +1,11 @@
 /**
- * Accessibility (a11y) functions, types, helpers
+ * Accessibility (a11y) functions, types, helpers.
+ *
  * @see https://www.w3.org/WAI/
  * @see https://www.w3.org/TR/wai-aria-1.1/
  * @see https://www.w3.org/TR/svg-aam-1.0/
- *
  */
-import { D3Element } from './mermaidAPI.js';
-
-import isEmpty from 'lodash-es/isEmpty.js';
+import type { D3Element } from './mermaidAPI.js';
 
 /**
  * SVG element role:
@@ -21,50 +19,47 @@ import isEmpty from 'lodash-es/isEmpty.js';
 const SVG_ROLE = 'graphics-document document';
 
 /**
- * Add role and aria-roledescription to the svg element
+ * Add role and aria-roledescription to the svg element.
  *
  * @param svg - d3 object that contains the SVG HTML element
  * @param diagramType - diagram name for to the aria-roledescription
  */
-export function setA11yDiagramInfo(svg: D3Element, diagramType: string | null | undefined) {
+export function setA11yDiagramInfo(svg: D3Element, diagramType: string) {
   svg.attr('role', SVG_ROLE);
-  if (!isEmpty(diagramType)) {
+  if (diagramType !== '') {
     svg.attr('aria-roledescription', diagramType);
   }
 }
+
 /**
  * Add an accessible title and/or description element to a chart.
  * The title is usually not displayed and the description is never displayed.
  *
- * The following charts display their title as a visual and accessibility element: gantt
+ * The following charts display their title as a visual and accessibility element: gantt.
  *
  * @param svg - d3 node to insert the a11y title and desc info
- * @param a11yTitle - a11y title. null and undefined are meaningful: means to skip it
- * @param a11yDesc - a11y description.  null and undefined are meaningful: means to skip it
+ * @param a11yTitle - a11y title. undefined or empty strings mean to skip them
+ * @param a11yDesc - a11y description. undefined or empty strings mean to skip them
  * @param baseId - id used to construct the a11y title and description id
  */
 export function addSVGa11yTitleDescription(
   svg: D3Element,
-  a11yTitle: string | null | undefined,
-  a11yDesc: string | null | undefined,
+  a11yTitle: string | undefined,
+  a11yDesc: string | undefined,
   baseId: string
-) {
+): void {
   if (svg.insert === undefined) {
     return;
   }
 
-  if (a11yTitle || a11yDesc) {
-    if (a11yDesc) {
-      const descId = 'chart-desc-' + baseId;
-      svg.attr('aria-describedby', descId);
-      svg.insert('desc', ':first-child').attr('id', descId).text(a11yDesc);
-    }
-    if (a11yTitle) {
-      const titleId = 'chart-title-' + baseId;
-      svg.attr('aria-labelledby', titleId);
-      svg.insert('title', ':first-child').attr('id', titleId).text(a11yTitle);
-    }
-  } else {
-    return;
+  if (a11yDesc) {
+    const descId = `chart-desc-${baseId}`;
+    svg.attr('aria-describedby', descId);
+    svg.insert('desc', ':first-child').attr('id', descId).text(a11yDesc);
+  }
+  if (a11yTitle) {
+    const titleId = `chart-title-${baseId}`;
+    svg.attr('aria-labelledby', titleId);
+    svg.insert('title', ':first-child').attr('id', titleId).text(a11yTitle);
   }
 }
diff --git a/packages/mermaid/src/mermaidAPI.spec.ts b/packages/mermaid/src/mermaidAPI.spec.ts
index 11c16827b9..0f4e614998 100644
--- a/packages/mermaid/src/mermaidAPI.spec.ts
+++ b/packages/mermaid/src/mermaidAPI.spec.ts
@@ -733,59 +733,7 @@ describe('mermaidAPI', () => {
           const diagramText = `${diagramType}\n accTitle: ${a11yTitle}\n accDescr: ${a11yDescr}\n`;
           const expectedDiagramType = testedDiagram.expectedType;
 
-          it('aria-roledscription is set to the diagram type, addSVGa11yTitleDescription is called', async () => {
-            const a11yDiagramInfo_spy = vi.spyOn(accessibility, 'setA11yDiagramInfo');
-            const a11yTitleDesc_spy = vi.spyOn(accessibility, 'addSVGa11yTitleDescription');
-            await mermaidAPI.render(id, diagramText);
-            expect(a11yDiagramInfo_spy).toHaveBeenCalledWith(
-              expect.anything(),
-              expectedDiagramType
-            );
-            expect(a11yTitleDesc_spy).toHaveBeenCalled();
-          });
-        });
-      });
-    });
-  });
-
-  describe('render', () => {
-    // Be sure to add async before each test (anonymous) method
-
-    // These are more like integration tests right now because nothing is mocked.
-    // But it is faster that a cypress test and there's no real reason to actually evaluate an image pixel by pixel.
-
-    // render(id, text, cb?, svgContainingElement?)
-
-    // Test all diagram types.  Note that old flowchart 'graph' type will invoke the flowRenderer-v2. (See the flowchart v2 detector.)
-    // We have to have both the specific textDiagramType and the expected type name because the expected type may be slightly different than was is put in the diagram text (ex: in -v2 diagrams)
-    const diagramTypesAndExpectations = [
-      { textDiagramType: 'C4Context', expectedType: 'c4' },
-      { textDiagramType: 'classDiagram', expectedType: 'classDiagram' },
-      { textDiagramType: 'classDiagram-v2', expectedType: 'classDiagram' },
-      { textDiagramType: 'erDiagram', expectedType: 'er' },
-      { textDiagramType: 'graph', expectedType: 'flowchart-v2' },
-      { textDiagramType: 'flowchart', expectedType: 'flowchart-v2' },
-      { textDiagramType: 'gitGraph', expectedType: 'gitGraph' },
-      { textDiagramType: 'gantt', expectedType: 'gantt' },
-      { textDiagramType: 'journey', expectedType: 'journey' },
-      { textDiagramType: 'pie', expectedType: 'pie' },
-      { textDiagramType: 'requirementDiagram', expectedType: 'requirement' },
-      { textDiagramType: 'sequenceDiagram', expectedType: 'sequence' },
-      { textDiagramType: 'stateDiagram-v2', expectedType: 'stateDiagram' },
-    ];
-
-    describe('accessibility', () => {
-      const id = 'mermaid-fauxId';
-      const a11yTitle = 'a11y title';
-      const a11yDescr = 'a11y description';
-
-      diagramTypesAndExpectations.forEach((testedDiagram) => {
-        describe(`${testedDiagram.textDiagramType}`, () => {
-          const diagramType = testedDiagram.textDiagramType;
-          const diagramText = `${diagramType}\n accTitle: ${a11yTitle}\n accDescr: ${a11yDescr}\n`;
-          const expectedDiagramType = testedDiagram.expectedType;
-
-          it('aria-roledscription is set to the diagram type, addSVGa11yTitleDescription is called', async () => {
+          it('should set aria-roledscription to the diagram type AND should call addSVGa11yTitleDescription', async () => {
             const a11yDiagramInfo_spy = vi.spyOn(accessibility, 'setA11yDiagramInfo');
             const a11yTitleDesc_spy = vi.spyOn(accessibility, 'addSVGa11yTitleDescription');
             await mermaidAPI.render(id, diagramText);
diff --git a/packages/mermaid/src/mermaidAPI.ts b/packages/mermaid/src/mermaidAPI.ts
index 753e4944ab..4d8d952906 100644
--- a/packages/mermaid/src/mermaidAPI.ts
+++ b/packages/mermaid/src/mermaidAPI.ts
@@ -478,7 +478,7 @@ const render = async function (
 
   // Get the temporary div element containing the svg
   const element = root.select(enclosingDivID_selector).node();
-  const graphType = diag.type;
+  const diagramType = diag.type;
 
   // -------------------------------------------------------------------------------
   // Create and insert the styles (user styles, theme styles, config styles)
@@ -486,11 +486,11 @@ const render = async function (
   // Insert an element into svg. This is where we put the styles
   const svg = element.firstChild;
   const firstChild = svg.firstChild;
-  const diagramClassDefs = CLASSDEF_DIAGRAMS.includes(graphType)
+  const diagramClassDefs = CLASSDEF_DIAGRAMS.includes(diagramType)
     ? diag.renderer.getClasses(text, diag)
     : {};
 
-  const rules = createUserStyles(config, graphType, diagramClassDefs, idSelector);
+  const rules = createUserStyles(config, diagramType, diagramClassDefs, idSelector);
 
   const style1 = document.createElement('style');
   style1.innerHTML = rules;
@@ -507,9 +507,9 @@ const render = async function (
 
   // This is the d3 node for the svg element
   const svgNode = root.select(`${enclosingDivID_selector} svg`);
-  const a11yTitle = diag.db.getAccTitle?.();
-  const a11yDescr = diag.db.getAccDescription?.();
-  addA11yInfo(graphType, svgNode, a11yTitle, a11yDescr);
+  const a11yTitle: string | undefined = diag.db.getAccTitle?.();
+  const a11yDescr: string | undefined = diag.db.getAccDescription?.();
+  addA11yInfo(diagramType, svgNode, a11yTitle, a11yDescr);
 
   // -------------------------------------------------------------------------------
   // Clean up SVG code
@@ -586,14 +586,18 @@ function initialize(options: MermaidConfig = {}) {
 /**
  * Add accessibility (a11y) information to the diagram.
  *
+ * @param diagramType - diagram type
+ * @param svgNode - d3 node to insert the a11y title and desc info
+ * @param a11yTitle - a11y title
+ * @param a11yDescr - a11y description
  */
 function addA11yInfo(
-  graphType: string,
+  diagramType: string,
   svgNode: D3Element,
-  a11yTitle: string | undefined,
-  a11yDescr: string | undefined
-) {
-  setA11yDiagramInfo(svgNode, graphType);
+  a11yTitle?: string,
+  a11yDescr?: string
+): void {
+  setA11yDiagramInfo(svgNode, diagramType);
   addSVGa11yTitleDescription(svgNode, a11yTitle, a11yDescr, svgNode.attr('id'));
 }
 
diff --git a/packages/mermaid/src/tests/MockedD3.ts b/packages/mermaid/src/tests/MockedD3.ts
index 6d8d721e0f..c5e080ba3d 100644
--- a/packages/mermaid/src/tests/MockedD3.ts
+++ b/packages/mermaid/src/tests/MockedD3.ts
@@ -1,5 +1,3 @@
-import type {} from '@vitest/spy/dist/index.js';
-
 /**
  * This is a mocked/stubbed version of the d3 Selection type. Each of the main functions are all
  * mocked (via vi.fn()) so you can track if they have been called, etc.
@@ -7,9 +5,8 @@ import type {} from '@vitest/spy/dist/index.js';
  * Note that node() returns a HTML Element with tag 'svg'. It is an empty element (no innerHTML, no children, etc).
  * This potentially allows testing of mermaidAPI render().
  */
-
 export class MockedD3 {
-  public attribs = new Map<string, string | null>();
+  public attribs = new Map<string, string>();
   public id: string | undefined = '';
   _children: MockedD3[] = [];
 
@@ -72,9 +69,9 @@ export class MockedD3 {
     return newMock;
   };
 
-  attr(attrName: string): null | undefined | string | number;
-  // attr(attrName: string, attrValue: string): MockedD3;
-  attr(attrName: string, attrValue?: string): null | undefined | string | number | MockedD3 {
+  attr(attrName: string): undefined | string;
+  attr(attrName: string, attrValue: string): MockedD3;
+  attr(attrName: string, attrValue?: string): undefined | string | MockedD3 {
     if (arguments.length === 1) {
       return this.attribs.get(attrName);
     } else {