Improve error log for wrong mandrel version and javaVersion comb.

Add test to test similar to the GraalVM one for the expected error
output.

__tests__/mandrel.test.ts

@@ -0,0 +1,56 @@
+import * as path from 'path'
+import * as mandrel from '../src/mandrel'
+import {expect, test} from '@jest/globals'
+import {getLatestRelease} from '../src/utils'
+
+process.env['RUNNER_TOOL_CACHE'] = path.join(__dirname, 'TOOL_CACHE')
+process.env['RUNNER_TEMP'] = path.join(__dirname, 'TEMP')
+
+test('request invalid version/javaVersion combination', async () => {
+  for (var combination of [
+    ['mandrel-23.1.1.0-Final', '17'],
+    ['mandrel-23.0.2.1-Final', '21'],
+  ]) {
+    let error = new Error('unexpected')
+    try {
+      await mandrel.setUpMandrel(combination[0], combination[1])
+    } catch (err) {
+      if (!(err instanceof Error)) {
+        fail(`Unexpected non-Error: ${err}`)
+      }
+      error = err
+    }
+
+    expect(error).not.toBeUndefined()
+    expect(error.message).toContain('Failed to download')
+    expect(error.message).toContain('Are you sure version')
+  }
+})
+test('request invalid version', async () => {
+  for (var combination of [
+    ['mandrel-23.1.1.0', '21'],
+    ['mandrel-23.0.2.1', '17'],
+  ]) {
+    let error = new Error('unexpected')
+    try {
+      await mandrel.setUpMandrel(combination[0], combination[1])
+    } catch (err) {
+      if (!(err instanceof Error)) {
+        fail(`Unexpected non-Error: ${err}`)
+      }
+      error = err
+    }
+
+    expect(error).not.toBeUndefined()
+    expect(error.message).toContain('Failed to download')
+    expect(error.message).toContain('Are you sure version')
+  }
+})
+
+test('find latest', async () => {
+  // Make sure the action can find the latest Mandrel release
+  const latestRelease = await getLatestRelease(mandrel.MANDREL_REPO)
+  const tag_name = latestRelease.tag_name
+  expect(tag_name).toContain(mandrel.MANDREL_TAG_PREFIX)
+})
+