diff --git a/plugins/plotly-express/src/js/jest.config.cjs b/plugins/plotly-express/src/js/jest.config.cjs
new file mode 100644
index 000000000..221b5070f
--- /dev/null
+++ b/plugins/plotly-express/src/js/jest.config.cjs
@@ -0,0 +1,7 @@
+const baseConfig = require('../../../../jest.config.base.cjs');
+const packageJson = require('./package');
+
+module.exports = {
+  ...baseConfig,
+  displayName: packageJson.name,
+};
diff --git a/plugins/plotly-express/src/js/src/PlotlyExpressChartUtils.test.ts b/plugins/plotly-express/src/js/src/PlotlyExpressChartUtils.test.ts
new file mode 100644
index 000000000..428e93793
--- /dev/null
+++ b/plugins/plotly-express/src/js/src/PlotlyExpressChartUtils.test.ts
@@ -0,0 +1,204 @@
+import {
+  getPathParts,
+  isLineSeries,
+  isAutoAxis,
+  isLinearAxis,
+  areSameAxisRange,
+  removeColorsFromData,
+  getDataMappings,
+  PlotlyChartWidgetData,
+} from './PlotlyExpressChartUtils';
+
+describe('getDataMappings', () => {
+  it('should return the data mappings from the widget data', () => {
+    const widgetData = {
+      type: 'test',
+      figure: {
+        deephaven: {
+          mappings: [
+            { table: 0, data_columns: { x: ['x0'], y: ['y0'] } },
+            { table: 1, data_columns: { x: ['x1'], y: ['y1'] } },
+          ],
+          is_user_set_color: false,
+          is_user_set_template: false,
+        },
+        plotly: {
+          data: [],
+        },
+      },
+      revision: 0,
+      new_references: [],
+      removed_references: [],
+    } satisfies PlotlyChartWidgetData;
+
+    const expectedMappings = new Map([
+      [
+        0,
+        new Map([
+          ['x', ['x0']],
+          ['y', ['y0']],
+        ]),
+      ],
+      [
+        1,
+        new Map([
+          ['x', ['x1']],
+          ['y', ['y1']],
+        ]),
+      ],
+    ]);
+
+    expect(getDataMappings(widgetData)).toEqual(expectedMappings);
+  });
+});
+
+describe('removeColorsFromData', () => {
+  it('should remove colors in the original colorway', () => {
+    const colorway = ['red', 'green', 'blue'];
+    const data = [
+      {
+        marker: {
+          color: 'red',
+        },
+      },
+      {
+        line: {
+          color: 'blue',
+        },
+      },
+    ];
+    const expectedData = [
+      {
+        marker: {},
+      },
+      {
+        line: {},
+      },
+    ];
+    removeColorsFromData(colorway, data);
+    expect(data).toEqual(expectedData);
+  });
+
+  it('should not remove colors that were not in the colorway', () => {
+    const colorway = ['red', 'green', 'blue'];
+    const data = [
+      {
+        marker: {
+          color: 'purple',
+        },
+      },
+      {
+        line: {
+          color: 'yellow',
+        },
+      },
+    ];
+    // Clone because the data should not be modified, but removeColorsFromData mutates the input
+    const expectedData = structuredClone(data);
+    removeColorsFromData(colorway, data);
+    expect(data).toEqual(expectedData);
+  });
+});
+
+describe('getPathParts', () => {
+  it('should return the path parts within the plotly data array', () => {
+    expect(getPathParts('/plotly/data/0/x')).toEqual(['0', 'x']);
+  });
+
+  it('should return an empty array if the path is empty', () => {
+    expect(getPathParts('')).toEqual([]);
+  });
+});
+
+describe('isLineSeries', () => {
+  it('should return true if the data is a line series without markers', () => {
+    expect(
+      isLineSeries({
+        type: 'scatter',
+        mode: 'lines',
+      })
+    ).toBe(true);
+
+    expect(
+      isLineSeries({
+        type: 'scattergl',
+        mode: 'lines',
+      })
+    ).toBe(true);
+  });
+
+  it('should return false if the data is not a line series without markers', () => {
+    expect(
+      isLineSeries({
+        type: 'scatter',
+        mode: 'lines+markers',
+      })
+    ).toBe(false);
+
+    expect(
+      isLineSeries({
+        type: 'scatterpolar',
+        mode: 'lines',
+      })
+    ).toBe(false);
+  });
+});
+
+describe('isAutoAxis', () => {
+  it('should return true if the axis type is automatically determined based on the data', () => {
+    expect(
+      isAutoAxis({
+        type: '-',
+      })
+    ).toBe(true);
+
+    expect(isAutoAxis({})).toBe(true);
+  });
+
+  it('should return false if the axis type is not automatically determined based on the data', () => {
+    expect(
+      isAutoAxis({
+        type: 'linear',
+      })
+    ).toBe(false);
+  });
+});
+
+describe('isLinearAxis', () => {
+  it('should return true if the axis is a linear axis', () => {
+    expect(
+      isLinearAxis({
+        type: 'linear',
+      })
+    ).toBe(true);
+
+    expect(
+      isLinearAxis({
+        type: 'date',
+      })
+    ).toBe(true);
+  });
+
+  it('should return false if the axis is not a linear axis', () => {
+    expect(
+      isLinearAxis({
+        type: 'log',
+      })
+    ).toBe(false);
+  });
+});
+
+describe('areSameAxisRange', () => {
+  it('should return true if the two axis ranges are null (autorange)', () => {
+    expect(areSameAxisRange(null, null)).toBe(true);
+  });
+  it('should return true if the two axis ranges are the same', () => {
+    expect(areSameAxisRange([0, 10], [0, 10])).toBe(true);
+  });
+  it('should return false if the two axis ranges are different', () => {
+    expect(areSameAxisRange([0, 10], [0, 20])).toBe(false);
+    expect(areSameAxisRange([0, 20], [0, 10])).toBe(false);
+    expect(areSameAxisRange([0, 10], null)).toBe(false);
+    expect(areSameAxisRange(null, [0, 10])).toBe(false);
+  });
+});