testing slots returns TypeError: Cannot convert undefined or null to object

[cbecker-tc]

I'm trying to test a very simple slot on a component. I've used the mounting option from the docs like this

   	wrapper = shallowMount(BaseIcon, {
   		propsData: {
   			title: "test",
   		},
   		slots: {
   			default: 'Main Content'
   		},
   		global: {
   			plugins: [i18n]
   		}
   	});

my template looks like this

<template>
    <svg
        xmlns="http://www.w3.org/2000/svg"
        :viewBox="viewBox"
        :height="height"
        :width="width"
        role="img">
        <title>{{ t(title) }}</title>
        <g :fill="fill">
            <slot />
        </g>
    </svg>
</template>

running the test returns this error:

1) BaseIcon slot content
       "before each" hook for "has the correct content":
     TypeError: Cannot convert undefined or null to object
      at render (eval at processSlot (dist/js/webpack:/node_modules/@vue/test-utils/dist/vue-test-utils.esm-bundler.js:259:1), <anonymous>:6:3)

can anyone help me pin down what I'm doing wrong?

[cbecker-tc]

We were able to solve it by changing the slot option to default: () => 'Main Content', but I'm not entirely sure why a string didn't work here.

[claranceliberi]

Works 1000%