Karma gives 404 for images (AureliaJS) - karma-runner

Question

Using the Aurelia CLI I run my unit tests with au test. Karma logs to console (over and over again for multiple requests):
WARN [web-server]: 404: /src/assets/images/avatar-backup.png
I understand that including my image files with tests isn't necessary and I could change the log levels to ignore these warnings, but this seems like it should really be a non issue. If for nothing else I want to know why and how to fix this for my own curiosity.
I've tried a combination of different methods found here and here (and elsewhere), but I still cannot figure out what I'm doing wrong. I'm still somewhat new to Karma and Aurelia so maybe I'm missing some fundamental understanding... I don't know.
Currently my this is my karma.conf.js
'use strict';
const path = require('path');
const project = require('./aurelia_project/aurelia.json');
const tsconfig = require('./tsconfig.json');
let testSrc = [
{ pattern: project.unitTestRunner.source, included: false },
'test/aurelia-karma.js'
];
let output = project.platform.output;
let appSrc = project.build.bundles.map(x => path.join(output, x.name));
let entryIndex = appSrc.indexOf(path.join(output, project.build.loader.configTarget));
let entryBundle = appSrc.splice(entryIndex, 1)[0];
// Added the image file sources
let imgFiles = [
{pattern: 'src/assets/images/*', watched: false, included: false, served: true, nocache: false},
// Added an exact path in case my pattern was somehow wrong, still doesn't load
{pattern: 'src/assets/images/avatar-backup.png', watched: false, included: false, served: true, nocache: false}
];
// Concat imgFiles to file array
let files = [entryBundle].concat(imgFiles).concat(testSrc).concat(appSrc);
module.exports = function(config) {
config.set({
basePath: '',
frameworks: [project.testFramework.id],
files: files,
exclude: [],
preprocessors: {
[project.unitTestRunner.source]: [project.transpiler.id]
},
typescriptPreprocessor: {
typescript: require('typescript'),
options: tsconfig.compilerOptions
},
reporters: ['progress'],
port: 9876,
colors: true,
logLevel: config.LOG_INFO,
autoWatch: true,
browsers: ['Chrome'],
singleRun: false,
// client.args must be a array of string.
// Leave 'aurelia-root', projectName.paths.root in this order so we can find
// the root of the aurelia projectName.
client: {
args: ['aurelia-root', project.paths.root]
},
browserConsoleLogOptions: {
terminal: true,
level: ""
},
// Not sure how to use proxy in combination with my added file sources or if I even need to...
// proxies: {
// "/img/": "http://localhost:9876/base/src/assets/images/"
// },
});
};
My app file structure looks like:
app
- src
- assets
- images
- (..images)
- test
- unit
- (..tests)