diff --git a/app/forms/idv/api_image_upload_form.rb b/app/forms/idv/api_image_upload_form.rb
index 98f421a7209..1f64925569d 100644
--- a/app/forms/idv/api_image_upload_form.rb
+++ b/app/forms/idv/api_image_upload_form.rb
@@ -75,16 +75,8 @@ def validate_images
     def validate_image(image_key)
       file = params[image_key]
 
-      unless file.respond_to?(:content_type)
-        errors.add(image_key, t('doc_auth.errors.not_a_file'))
-        return
-      end
-
-      data = file.read
-      file.rewind
-
-      return if file.content_type.start_with?('image/') && data.present?
-      errors.add(image_key, t('doc_auth.errors.must_be_image'))
+      return if file.respond_to?(:read)
+      errors.add(image_key, t('doc_auth.errors.not_a_file'))
     end
   end
 end
diff --git a/app/javascript/packages/document-capture/components/acuant-capture.jsx b/app/javascript/packages/document-capture/components/acuant-capture.jsx
index 05f1585b92a..ef69f979c77 100644
--- a/app/javascript/packages/document-capture/components/acuant-capture.jsx
+++ b/app/javascript/packages/document-capture/components/acuant-capture.jsx
@@ -15,6 +15,7 @@ import Button from './button';
 import useI18n from '../hooks/use-i18n';
 import DeviceContext from '../context/device';
 import FileBase64CacheContext from '../context/file-base64-cache';
+import UploadContext from '../context/upload';
 
 /** @typedef {import('react').ReactNode} ReactNode */
 
@@ -28,9 +29,6 @@ import FileBase64CacheContext from '../context/file-base64-cache';
  * @prop {'user'|'environment'=} capture Facing mode of capture. If capture is not specified and a
  * camera is supported, defaults to the Acuant environment camera capture.
  * @prop {string=} className Optional additional class names.
- * @prop {number=} minimumGlareScore Minimum glare score to be considered acceptable.
- * @prop {number=} minimumSharpnessScore Minimum sharpness score to be considered acceptable.
- * @prop {number=} minimumFileSize Minimum file size (in bytes) to be considered acceptable.
  * @prop {boolean=} allowUpload Whether to allow file upload. Defaults to `true`.
  * @prop {ReactNode=} errorMessage Error to show.
  */
@@ -40,24 +38,33 @@ import FileBase64CacheContext from '../context/file-base64-cache';
  *
  * @type {number}
  */
-const DEFAULT_ACCEPTABLE_GLARE_SCORE = 50;
+const ACCEPTABLE_GLARE_SCORE = 50;
 
 /**
  * The minimum sharpness score value to be considered acceptable.
  *
  * @type {number}
  */
-const DEFAULT_ACCEPTABLE_SHARPNESS_SCORE = 50;
+const ACCEPTABLE_SHARPNESS_SCORE = 50;
 
 /**
  * The minimum file size (bytes) for an image to be considered acceptable.
  *
  * @type {number}
  */
-const DEFAULT_ACCEPTABLE_FILE_SIZE_BYTES =
-  process.env.ACUANT_MINIMUM_FILE_SIZE === undefined
-    ? 250 * 1024
-    : Number(process.env.ACUANT_MINIMUM_FILE_SIZE);
+export const ACCEPTABLE_FILE_SIZE_BYTES = 250 * 1024;
+
+/**
+ * Given a file, returns minimum acceptable file size in bytes, depending on the type of file and
+ * the current environment.
+ *
+ * @param {Blob} file File to assess.
+ *
+ * @return {number} Minimum file size, in bytes.
+ */
+export function getMinimumFileSize(file) {
+  return file.type.startsWith('image/') ? ACCEPTABLE_FILE_SIZE_BYTES : 0;
+}
 
 /**
  * Returns an instance of File representing the given data URL.
@@ -90,9 +97,6 @@ function AcuantCapture(
     onChange = () => {},
     capture,
     className,
-    minimumGlareScore = DEFAULT_ACCEPTABLE_GLARE_SCORE,
-    minimumSharpnessScore = DEFAULT_ACCEPTABLE_SHARPNESS_SCORE,
-    minimumFileSize = DEFAULT_ACCEPTABLE_FILE_SIZE_BYTES,
     allowUpload = true,
     errorMessage,
   },
@@ -100,6 +104,7 @@ function AcuantCapture(
 ) {
   const fileCache = useContext(FileBase64CacheContext);
   const { isReady, isError, isCameraSupported } = useContext(AcuantContext);
+  const { isMockClient } = useContext(UploadContext);
   const inputRef = useRef(/** @type {?HTMLInputElement} */ (null));
   const isForceUploading = useRef(false);
   const [isCapturing, setIsCapturing] = useState(false);
@@ -151,7 +156,7 @@ function AcuantCapture(
    * @param {Blob?} nextValue Next value candidate.
    */
   function onChangeIfValid(nextValue) {
-    if (nextValue && nextValue.size < minimumFileSize) {
+    if (nextValue && nextValue.size < getMinimumFileSize(nextValue)) {
       setOwnErrorMessage(t('errors.doc_auth.photo_file_size'));
     } else {
       setOwnErrorMessage(null);
@@ -190,9 +195,9 @@ function AcuantCapture(
         <FullScreen onRequestClose={() => setIsCapturing(false)}>
           <AcuantCaptureCanvas
             onImageCaptureSuccess={(nextCapture) => {
-              if (nextCapture.glare < minimumGlareScore) {
+              if (nextCapture.glare < ACCEPTABLE_GLARE_SCORE) {
                 setOwnErrorMessage(t('errors.doc_auth.photo_glare'));
-              } else if (nextCapture.sharpness < minimumSharpnessScore) {
+              } else if (nextCapture.sharpness < ACCEPTABLE_SHARPNESS_SCORE) {
                 setOwnErrorMessage(t('errors.doc_auth.photo_blurry'));
               } else {
                 const dataAsBlob = toBlob(nextCapture.image.data);
@@ -214,7 +219,7 @@ function AcuantCapture(
         label={label}
         hint={hasCapture || !allowUpload ? undefined : t('doc_auth.tips.document_capture_hint')}
         bannerText={bannerText}
-        accept={['image/*']}
+        accept={isMockClient ? undefined : ['image/*']}
         capture={capture}
         value={value}
         errorMessage={ownErrorMessage ?? errorMessage}
diff --git a/app/javascript/packages/document-capture/components/submission.jsx b/app/javascript/packages/document-capture/components/submission.jsx
index 1678b2b647e..cae65ed0a18 100644
--- a/app/javascript/packages/document-capture/components/submission.jsx
+++ b/app/javascript/packages/document-capture/components/submission.jsx
@@ -17,7 +17,7 @@ import CallbackOnMount from './callback-on-mount';
  * @param {SubmissionProps} props Props object.
  */
 function Submission({ payload, onError }) {
-  const upload = useContext(UploadContext);
+  const { upload } = useContext(UploadContext);
   const resource = useAsync(upload, payload);
 
   return (
diff --git a/app/javascript/packages/document-capture/context/upload.jsx b/app/javascript/packages/document-capture/context/upload.jsx
index 24c19488560..fd019ee082a 100644
--- a/app/javascript/packages/document-capture/context/upload.jsx
+++ b/app/javascript/packages/document-capture/context/upload.jsx
@@ -1,7 +1,10 @@
-import React, { createContext } from 'react';
+import React, { createContext, useMemo } from 'react';
 import defaultUpload from '../services/upload';
 
-const UploadContext = createContext(defaultUpload);
+const UploadContext = createContext({
+  upload: defaultUpload,
+  isMockClient: false,
+});
 
 /** @typedef {import('react').ReactNode} ReactNode */
 
@@ -45,6 +48,7 @@ const UploadContext = createContext(defaultUpload);
  * @typedef UploadContextProviderProps
  *
  * @prop {UploadImplementation=} upload Custom upload implementation.
+ * @prop {boolean=} isMockClient Whether to treat upload as a mock implementation.
  * @prop {string} endpoint Endpoint to which payload should be sent.
  * @prop {string} csrf CSRF token to send as parameter to upload implementation.
  * @prop {Record<string,any>} formData Extra form data to merge into the payload before uploading
@@ -54,10 +58,18 @@ const UploadContext = createContext(defaultUpload);
 /**
  * @param {UploadContextProviderProps} props Props object.
  */
-function UploadContextProvider({ upload = defaultUpload, endpoint, csrf, formData, children }) {
+function UploadContextProvider({
+  upload = defaultUpload,
+  isMockClient = false,
+  endpoint,
+  csrf,
+  formData,
+  children,
+}) {
   const uploadWithCSRF = (payload) => upload({ ...payload, ...formData }, { endpoint, csrf });
+  const value = useMemo(() => ({ upload: uploadWithCSRF, isMockClient }), [upload, isMockClient]);
 
-  return <UploadContext.Provider value={uploadWithCSRF}>{children}</UploadContext.Provider>;
+  return <UploadContext.Provider value={value}>{children}</UploadContext.Provider>;
 }
 
 export default UploadContext;
diff --git a/app/javascript/packs/document-capture.jsx b/app/javascript/packs/document-capture.jsx
index 8af4b90115c..49417446af0 100644
--- a/app/javascript/packs/document-capture.jsx
+++ b/app/javascript/packs/document-capture.jsx
@@ -27,6 +27,7 @@ document.body.classList.add('js-skip-form-validation');
 loadPolyfills(['fetch']).then(() => {
   const appRoot = document.getElementById('document-capture-form');
   const isLivenessEnabled = appRoot.hasAttribute('data-liveness');
+  const isMockClient = appRoot.hasAttribute('data-mock-client');
 
   render(
     <AcuantProvider
@@ -36,6 +37,7 @@ loadPolyfills(['fetch']).then(() => {
       <UploadContextProvider
         endpoint={appRoot.getAttribute('data-endpoint')}
         csrf={getMetaContent('csrf-token')}
+        isMockClient={isMockClient}
         formData={{
           document_capture_session_uuid: appRoot.getAttribute('data-document-capture-session-uuid'),
           locale: i18n.currentLocale(),
diff --git a/app/views/idv/shared/_document_capture.html.erb b/app/views/idv/shared/_document_capture.html.erb
index 7218a4d6f24..17e27920398 100644
--- a/app/views/idv/shared/_document_capture.html.erb
+++ b/app/views/idv/shared/_document_capture.html.erb
@@ -12,6 +12,7 @@
   <% end %>
   <%= tag.div id: 'document-capture-form', data: {
     liveness: liveness_checking_enabled?.presence,
+    mock_client: (DocAuth::Client.doc_auth_vendor == 'mock').presence,
     document_capture_session_uuid: flow_session[:document_capture_session_uuid],
     endpoint: api_verify_images_url
   } %>
diff --git a/config/locales/doc_auth/en.yml b/config/locales/doc_auth/en.yml
index 454f16fc031..465b78512ab 100644
--- a/config/locales/doc_auth/en.yml
+++ b/config/locales/doc_auth/en.yml
@@ -13,7 +13,6 @@ en:
       upload_picture: Upload a photo
       use_phone: Use your phone
     errors:
-      must_be_image: File must be an image
       not_a_file: The selection was not a valid file
     forms:
       address1: Address
diff --git a/config/locales/doc_auth/es.yml b/config/locales/doc_auth/es.yml
index 3378797a4fd..89754a0462b 100644
--- a/config/locales/doc_auth/es.yml
+++ b/config/locales/doc_auth/es.yml
@@ -13,7 +13,6 @@ es:
       upload_picture: Sube una foto
       use_phone: Usa tu telefono
     errors:
-      must_be_image: El archivo debe ser una imagen
       not_a_file: La selección no era un archivo válido
     forms:
       address1: Dirección
diff --git a/config/locales/doc_auth/fr.yml b/config/locales/doc_auth/fr.yml
index 003ead2762d..b210accf89b 100644
--- a/config/locales/doc_auth/fr.yml
+++ b/config/locales/doc_auth/fr.yml
@@ -13,7 +13,6 @@ fr:
       upload_picture: Télécharger une photo
       use_phone: Utilisez votre téléphone
     errors:
-      must_be_image: Le fichier doit être une image
       not_a_file: La sélection n'était pas un fichier valide
     forms:
       address1: Adresse
diff --git a/spec/controllers/idv/image_uploads_controller_spec.rb b/spec/controllers/idv/image_uploads_controller_spec.rb
index c3ddf7fd26f..0ff0b00eb1a 100644
--- a/spec/controllers/idv/image_uploads_controller_spec.rb
+++ b/spec/controllers/idv/image_uploads_controller_spec.rb
@@ -108,6 +108,22 @@
           ]
         end
       end
+
+      context 'when a value is an error-formatted yaml file' do
+        before { params.merge!(back: DocAuthImageFixtures.error_yaml_multipart) }
+
+        it 'returns error from yaml file' do
+          action
+
+          json = JSON.parse(response.body, symbolize_names: true)
+          expect(json[:errors]).to eq [
+            {
+              field: 'results',
+              message: I18n.t('friendly_errors.doc_auth.barcode_could_not_be_read'),
+            },
+          ]
+        end
+      end
     end
   end
 end
diff --git a/spec/forms/idv/api_image_upload_form_spec.rb b/spec/forms/idv/api_image_upload_form_spec.rb
index c8a0e0105d5..7e3b4dffe44 100644
--- a/spec/forms/idv/api_image_upload_form_spec.rb
+++ b/spec/forms/idv/api_image_upload_form_spec.rb
@@ -59,33 +59,6 @@
       end
     end
 
-    context 'when file does not have an image content type' do
-      let(:tempfile) do
-        Tempfile.new.tap do |f|
-          f.write('test')
-          f.close
-        end
-      end
-      let(:selfie_image) { Rack::Test::UploadedFile.new(tempfile.path, 'text/plain') }
-
-      it 'is not valid' do
-        expect(form.valid?).to eq(false)
-        expect(form.errors[:selfie]).to eq(['File must be an image'])
-      end
-    end
-
-    context 'when file is empty' do
-      let(:tempfile) { Tempfile.new }
-      let(:selfie_image) { Rack::Test::UploadedFile.new(tempfile.path, 'image/jpeg') }
-
-      it 'is not valid' do
-        expect(form.valid?).to eq(false)
-        expect(form.errors[:selfie]).to eq(['File must be an image'])
-      end
-
-      after { tempfile.unlink }
-    end
-
     context 'when document_capture_session_uuid param is missing' do
       let(:document_capture_session_uuid) { nil }
 
diff --git a/spec/javascripts/packages/document-capture/components/acuant-capture-spec.jsx b/spec/javascripts/packages/document-capture/components/acuant-capture-spec.jsx
index 8904b93d84e..bf7b2ec3b9f 100644
--- a/spec/javascripts/packages/document-capture/components/acuant-capture-spec.jsx
+++ b/spec/javascripts/packages/document-capture/components/acuant-capture-spec.jsx
@@ -3,15 +3,32 @@ import { fireEvent } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
 import { waitForElementToBeRemoved } from '@testing-library/dom';
 import sinon from 'sinon';
-import AcuantCapture from '@18f/identity-document-capture/components/acuant-capture';
+import AcuantCapture, {
+  getMinimumFileSize,
+  ACCEPTABLE_FILE_SIZE_BYTES,
+} from '@18f/identity-document-capture/components/acuant-capture';
 import { Provider as AcuantContextProvider } from '@18f/identity-document-capture/context/acuant';
 import DeviceContext from '@18f/identity-document-capture/context/device';
 import I18nContext from '@18f/identity-document-capture/context/i18n';
 import render from '../../../support/render';
 import { useAcuant } from '../../../support/acuant';
+import { useSandbox } from '../../../support/sinon';
 
 describe('document-capture/components/acuant-capture', () => {
   const { initialize } = useAcuant();
+  const sandbox = useSandbox();
+
+  describe('getMinimumFileSize', () => {
+    it('returns zero for non-image file', () => {
+      const file = new window.File([], 'file.yml', { type: 'application/x-yaml' });
+      expect(getMinimumFileSize(file)).to.equal(0);
+    });
+
+    it('returns non-zero for image file', () => {
+      const file = new window.File([], 'file.png', { type: 'image/png' });
+      expect(getMinimumFileSize(file)).to.be.gt(0);
+    });
+  });
 
   context('mobile', () => {
     it('renders with assumed capture button support while acuant is not ready and on mobile', () => {
@@ -146,6 +163,8 @@ describe('document-capture/components/acuant-capture', () => {
     });
 
     it('calls onChange with the captured image on successful capture', async () => {
+      sandbox.stub(window.Blob.prototype, 'size').value(ACCEPTABLE_FILE_SIZE_BYTES);
+
       const onChange = sinon.mock();
       const { getByText } = render(
         <DeviceContext.Provider value={{ isMobile: true }}>
@@ -311,6 +330,7 @@ describe('document-capture/components/acuant-capture', () => {
             <AcuantCapture label="Image" />
           </AcuantContextProvider>
         </DeviceContext.Provider>,
+        { isMockClient: false },
       );
 
       initialize({
@@ -343,6 +363,8 @@ describe('document-capture/components/acuant-capture', () => {
     });
 
     it('removes error message once image is corrected', async () => {
+      sandbox.stub(window.Blob.prototype, 'size').value(ACCEPTABLE_FILE_SIZE_BYTES);
+
       const { getByText, findByText } = render(
         <DeviceContext.Provider value={{ isMobile: true }}>
           <AcuantContextProvider sdkSrc="about:blank">
@@ -602,4 +624,17 @@ describe('document-capture/components/acuant-capture', () => {
     expect(defaultPrevented).to.be.false();
     expect(window.AcuantCameraUI.start.called).to.be.false();
   });
+
+  it('restricts accepted file types', () => {
+    const { getByLabelText } = render(
+      <AcuantContextProvider sdkSrc="about:blank">
+        <AcuantCapture label="Image" capture="environment" />
+      </AcuantContextProvider>,
+      { isMockClient: false },
+    );
+
+    const input = getByLabelText('Image');
+
+    expect(input.getAttribute('accept')).to.equal('image/*');
+  });
 });
diff --git a/spec/javascripts/packages/document-capture/components/document-capture-spec.jsx b/spec/javascripts/packages/document-capture/components/document-capture-spec.jsx
index 1fd1ede7076..fd23d830615 100644
--- a/spec/javascripts/packages/document-capture/components/document-capture-spec.jsx
+++ b/spec/javascripts/packages/document-capture/components/document-capture-spec.jsx
@@ -2,6 +2,7 @@ import React from 'react';
 import userEvent from '@testing-library/user-event';
 import { waitFor } from '@testing-library/dom';
 import { fireEvent } from '@testing-library/react';
+import { ACCEPTABLE_FILE_SIZE_BYTES } from '@18f/identity-document-capture/components/acuant-capture';
 import { UploadFormEntriesError } from '@18f/identity-document-capture/services/upload';
 import { AcuantProvider, DeviceContext } from '@18f/identity-document-capture';
 import DocumentCapture, {
@@ -9,9 +10,11 @@ import DocumentCapture, {
 } from '@18f/identity-document-capture/components/document-capture';
 import render from '../../../support/render';
 import { useAcuant } from '../../../support/acuant';
+import { useSandbox } from '../../../support/sinon';
 
 describe('document-capture/components/document-capture', () => {
   const { initialize } = useAcuant();
+  const sandbox = useSandbox();
 
   function isFormValid(form) {
     return [...form.querySelectorAll('input')].every((input) => input.checkValidity());
@@ -21,6 +24,7 @@ describe('document-capture/components/document-capture', () => {
 
   beforeEach(() => {
     originalHash = window.location.hash;
+    sandbox.stub(window.Blob.prototype, 'size').value(ACCEPTABLE_FILE_SIZE_BYTES);
   });
 
   afterEach(() => {
diff --git a/spec/javascripts/packages/document-capture/components/documents-step-spec.jsx b/spec/javascripts/packages/document-capture/components/documents-step-spec.jsx
index 9583a310493..439cf273fa9 100644
--- a/spec/javascripts/packages/document-capture/components/documents-step-spec.jsx
+++ b/spec/javascripts/packages/document-capture/components/documents-step-spec.jsx
@@ -1,12 +1,20 @@
 import React from 'react';
 import userEvent from '@testing-library/user-event';
 import sinon from 'sinon';
+import { ACCEPTABLE_FILE_SIZE_BYTES } from '@18f/identity-document-capture/components/acuant-capture';
 import DeviceContext from '@18f/identity-document-capture/context/device';
 import DocumentsStep, { validate } from '@18f/identity-document-capture/components/documents-step';
 import { RequiredValueMissingError } from '@18f/identity-document-capture/components/form-steps';
 import render from '../../../support/render';
+import { useSandbox } from '../../../support/sinon';
 
 describe('document-capture/components/documents-step', () => {
+  const sandbox = useSandbox();
+
+  beforeEach(() => {
+    sandbox.stub(window.Blob.prototype, 'size').value(ACCEPTABLE_FILE_SIZE_BYTES);
+  });
+
   describe('validate', () => {
     it('returns errors if both front and back are unset', () => {
       const value = {};
@@ -58,15 +66,6 @@ describe('document-capture/components/documents-step', () => {
     expect(onChange.getCall(0).args[0]).to.deep.equal({ front: file });
   });
 
-  it('restricts accepted file types', () => {
-    const onChange = sinon.spy();
-    const { getByLabelText } = render(<DocumentsStep onChange={onChange} />);
-
-    const input = getByLabelText('doc_auth.headings.document_capture_front');
-
-    expect(input.getAttribute('accept')).to.equal('image/*');
-  });
-
   it('renders device-specific instructions', () => {
     let { getByText } = render(
       <DeviceContext.Provider value={{ isMobile: true }}>
diff --git a/spec/javascripts/packages/document-capture/components/selfie-step-spec.jsx b/spec/javascripts/packages/document-capture/components/selfie-step-spec.jsx
index 52692d6418c..498ab98816b 100644
--- a/spec/javascripts/packages/document-capture/components/selfie-step-spec.jsx
+++ b/spec/javascripts/packages/document-capture/components/selfie-step-spec.jsx
@@ -1,11 +1,19 @@
 import React from 'react';
 import userEvent from '@testing-library/user-event';
 import sinon from 'sinon';
+import { ACCEPTABLE_FILE_SIZE_BYTES } from '@18f/identity-document-capture/components/acuant-capture';
 import SelfieStep, { validate } from '@18f/identity-document-capture/components/selfie-step';
 import { RequiredValueMissingError } from '@18f/identity-document-capture/components/form-steps';
 import render from '../../../support/render';
+import { useSandbox } from '../../../support/sinon';
 
 describe('document-capture/components/selfie-step', () => {
+  const sandbox = useSandbox();
+
+  beforeEach(() => {
+    sandbox.stub(window.Blob.prototype, 'size').value(ACCEPTABLE_FILE_SIZE_BYTES);
+  });
+
   describe('validate', () => {
     it('returns object with error if selfie is unset', () => {
       const value = {};
@@ -35,13 +43,4 @@ describe('document-capture/components/selfie-step', () => {
 
     expect(onChange.getCall(0).args[0]).to.deep.equal({ selfie: file });
   });
-
-  it('restricts accepted file types', () => {
-    const onChange = sinon.spy();
-    const { getByLabelText } = render(<SelfieStep onChange={onChange} />);
-
-    const input = getByLabelText('doc_auth.headings.document_capture_selfie');
-
-    expect(input.getAttribute('accept')).to.equal('image/*');
-  });
 });
diff --git a/spec/javascripts/packages/document-capture/context/upload-spec.jsx b/spec/javascripts/packages/document-capture/context/upload-spec.jsx
index c0d6163d9cd..fb4f0414ca3 100644
--- a/spec/javascripts/packages/document-capture/context/upload-spec.jsx
+++ b/spec/javascripts/packages/document-capture/context/upload-spec.jsx
@@ -10,8 +10,9 @@ describe('document-capture/context/upload', () => {
   it('defaults to the default upload service', () => {
     baseRender(
       createElement(() => {
-        const upload = useContext(UploadContext);
+        const { upload, isMockClient } = useContext(UploadContext);
         expect(upload).to.equal(defaultUpload);
+        expect(isMockClient).to.equal(false);
         return null;
       }),
     );
@@ -21,7 +22,7 @@ describe('document-capture/context/upload', () => {
     render(
       <UploadContextProvider upload={(payload) => Promise.resolve({ ...payload, received: true })}>
         {createElement(() => {
-          const upload = useContext(UploadContext);
+          const { upload } = useContext(UploadContext);
           useEffect(() => {
             upload({ sent: true }).then((result) => {
               expect(result).to.deep.equal({ sent: true, received: true });
@@ -34,6 +35,18 @@ describe('document-capture/context/upload', () => {
     );
   });
 
+  it('can be overridden with isMockClient value', () => {
+    render(
+      <UploadContextProvider isMockClient>
+        {createElement(() => {
+          const { isMockClient } = useContext(UploadContext);
+          expect(isMockClient).to.equal(true);
+          return null;
+        })}
+      </UploadContextProvider>,
+    );
+  });
+
   it('can provide endpoint and csrf to make available to uploader', (done) => {
     render(
       <UploadContextProvider
@@ -48,7 +61,7 @@ describe('document-capture/context/upload', () => {
         endpoint="https://example.com"
       >
         {createElement(() => {
-          const upload = useContext(UploadContext);
+          const { upload } = useContext(UploadContext);
           useEffect(() => {
             upload({ sent: true }).then((result) => {
               expect(result).to.deep.equal({
@@ -72,7 +85,7 @@ describe('document-capture/context/upload', () => {
         formData={{ foo: 'bar' }}
       >
         {createElement(() => {
-          const upload = useContext(UploadContext);
+          const { upload } = useContext(UploadContext);
           useEffect(() => {
             upload({ sent: true }).then((result) => {
               expect(result).to.deep.equal({
diff --git a/spec/javascripts/spec_helper.js b/spec/javascripts/spec_helper.js
index cb5b08a4a81..467148a7d9f 100644
--- a/spec/javascripts/spec_helper.js
+++ b/spec/javascripts/spec_helper.js
@@ -18,7 +18,5 @@ global.document = window.document;
 global.getComputedStyle = window.getComputedStyle;
 global.self = window;
 
-process.env.ACUANT_MINIMUM_FILE_SIZE = '0';
-
 useCleanDOM();
 useConsoleLogSpy();
diff --git a/spec/javascripts/support/render.jsx b/spec/javascripts/support/render.jsx
index bb6ee10b948..f5384fe666a 100644
--- a/spec/javascripts/support/render.jsx
+++ b/spec/javascripts/support/render.jsx
@@ -9,6 +9,7 @@ import { UploadContextProvider } from '@18f/identity-document-capture';
  * @typedef RenderOptions
  *
  * @prop {Error=} uploadError Whether to simulate upload failure.
+ * @prop {boolean=} isMockClient Whether to treat upload as a mock implementation.
  * @prop {number=} expectedUploads Number of times upload is expected to be called. Defaults to `1`.
  */
 
@@ -24,7 +25,7 @@ import { UploadContextProvider } from '@18f/identity-document-capture';
  * @return {import('@testing-library/react').RenderResult}
  */
 function renderWithDefaultContext(element, options = {}) {
-  const { uploadError, expectedUploads = 1, ...baseRenderOptions } = options;
+  const { uploadError, expectedUploads = 1, isMockClient = true, ...baseRenderOptions } = options;
 
   const upload = sinon
     .stub()
@@ -41,7 +42,9 @@ function renderWithDefaultContext(element, options = {}) {
   return render(element, {
     ...baseRenderOptions,
     wrapper: ({ children }) => (
-      <UploadContextProvider upload={upload}>{children}</UploadContextProvider>
+      <UploadContextProvider upload={upload} isMockClient={isMockClient}>
+        {children}
+      </UploadContextProvider>
     ),
   });
 }
diff --git a/spec/support/doc_auth_image_fixtures.rb b/spec/support/doc_auth_image_fixtures.rb
index 88a5fea50fc..8bf0dc598d7 100644
--- a/spec/support/doc_auth_image_fixtures.rb
+++ b/spec/support/doc_auth_image_fixtures.rb
@@ -31,6 +31,14 @@ def self.selfie_image_multipart
     Rack::Test::UploadedFile.new(fixture_path('selfie.jpg'), 'image/jpeg')
   end
 
+  def self.error_yaml_multipart
+    path = File.join(
+      File.dirname(__FILE__),
+      '../fixtures/ial2_test_credential_forces_error.yml',
+    )
+    Rack::Test::UploadedFile.new(path, Mime[:yaml])
+  end
+
   def self.fixture_path(filename)
     File.join(
       File.dirname(__FILE__),