What a Mock Interview Is, and How to Build a Real One

The formats the firms publish, and what a mock case must match

Two of the three largest firms describe their process in incompatible shapes, and both descriptions are on their own careers pages.

McKinsey's interviewing page is explicit that the shape is not fixed. Your interview experience will differ depending on the role for which you apply, it says, and several paths include an online assessment, a writing test or a group exercise. It then states the floor: all candidates have at least one individual interview, and the number of colleagues you meet will vary.

BCG's interview process page gives the opposite kind of description, four numbered steps ending in a team interview. So a mock consisting of one forty-minute case rehearses BCG's third step and none of McKinsey's variations.

The published cases row is the one that moved on 5 October 2026, and the section below says what BCG publishes and where it sits.

The feedback row is the one that decides how much a mock is worth. Bain's hiring process page says you will learn how each interview went. McKinsey and BCG publish no such promise, so for those two your mock is the only structured feedback you will receive before a decision.

OneDay@BCG, written by BCG and served elsewhere

BCG does publish case material. This page said it published none until 5 October 2026, and that was wrong. The firm announces it from its own case interview preparation page, under the heading "Put Your Skills to the Test": "Experience a day in the life of a consultant with OneDay@BCG, a free job simulation that provides insights into the challenges we solve."

Two facts travel together here and neither of them stands alone. The content is written by BCG and announced from the firm's own preparation page. It is served by a third party, theforage.com, which is where you work through it and where the files sit.

The scale is on the firm's virtual experience page: "With 13 unique modules to choose from" and "Enroll today and join the 700,000+ participants". The strategy module is a full case in seven tasks on a fictional client. It opens: "Today, you'll help us by stepping into the shoes of a BCG consultant to support our client, BeyondTech, a global technology and telecommunications leader" and asks "Is installment financing a viable option for BeyondTech?". The attachments open without an account: a three page PDF of income statements and balance sheets, a workbook, and a slide template. The payload carries Model Answer blocks and multiple choice questions with their corrections. At least eight of the thirteen modules name a fictional client, among them ClothingCo, RetailCo, CoffeeCo, PowerCo, SuperCo and NewCo.

Three things the source does not say, and each one changes how you use it. BCG never calls these modules case interviews, and nowhere says they resemble the case it runs in selection. The pages carry the line "No grades · No assessments". And the firm attaches a clause: "This virtual experience is not an employment relationship with BCG", followed by "It is our policy that you do not list your engagement as employment, work experience or an internship with BCG on your CV, LinkedIn profile, or any other social media or professional networking platform."

So for a mock, the strategy module supplies a prompt, data and a model answer, which is what step seven of the script below needs. What it does not supply is a rehearsal of BCG's selection case, because the firm never claims the two are alike.

The conditions you control in a mock case, down to handwriting

McKinsey's assessment integrity expectations are written as rules for candidates and read as a specification for a realistic mock. Adopt them from the first mock onward.

The framing rule is the one that changes behavior. The firm says it may ask to review your notes during the interview to understand your thought process, and it requires the camera to show your hands as you write. That makes legible handwriting part of the exercise, which nobody practices and which shows up badly at speed.

The calculator rule matters twice. It applies in interviews across the firms we read, and Bain states that calculators are allowed on its digital assessment only and not during any subsequent interviews. A mock run with a calculator on the desk has rehearsed a different task.

The mock case interview script for your interviewer

Hand this to whoever is running the mock. It works whether or not they know consulting, because the published cases carry their own answers.

1. Read the prompt once, then stop. Answer clarifying questions from the page. When the page is silent, say the page does not say.
2. Start a timer and stay quiet. Bain's published case gives the candidate one to two minutes to think; anything beyond that is a data point to note rather than a cue to help.
3. Ask for the structure to be walked through step by step. Bain's own wording asks candidates to walk the interviewer through the structure and analysis step by step.
4. Hand over the exhibit without introducing it. Then say nothing for thirty seconds.
5. Interrupt once, at a pre-agreed moment. Either why that branch first, or what does that number mean.
6. Ask for a recommendation in thirty seconds, then ask one hostile follow-up.
7. Read the published answer aloud. For Bain's case, read both the good answer and the better one.

Step seven is the reason a non-expert can run this. Bain labels a good answer as one including different types of ways to increase revenue and a better answer as one adding the pros, cons and practicality of each idea. The comparison does the assessing.

The mock case debrief, twenty minutes

Run the debrief on artifacts rather than impressions. Ours below, with the weights from our own grading code; no firm publishes a mark scheme.

Then two questions for the interviewer, which are the only two worth asking a non-expert.

1. What did I say that you did not understand? They are the authority on this and you are not.
2. Where did I go quiet, and for how long? BCG lists staying silent among the behaviors to avoid, and you will underestimate the duration every time.

What a mock case interview is worth, and when it stops

No firm publishes a number and we have not measured one, so the schedule below is ours. It is built around the observation that mocks stop being useful once they stop being uncomfortable.

The last row is deliberate. A bad mock two days out costs you more in confidence than it returns in learning, and our last minute case prep page covers what that time is actually for.

Change interviewer in the final week if you can. The value of a mock is concentrated in the unfamiliarity, and a fourth session with the same person rehearses a relationship rather than a round.

Mock interviews for the formats that are not cases

Two published formats need a different rehearsal and usually get none.

McKinsey states that several interview paths include a writing test or a group exercise. Neither is rehearsed by a one-to-one case, and the firm publishes no material for either, so the honest position is that you can rehearse the conditions and not the content.

EY's interview tips page describes prerecorded video interviews, where candidates record responses to questions sent in advance. That format has no interviewer at all, so a mock means recording yourself against a timer. EY adds the constraint that matters there: practice your stories out loud, and avoid reading from a script.

The group exercise is the format most worth improvising a rehearsal for, because its failure modes are social rather than analytical. Three people who have each prepared a structure will talk over one another, and BCG's published list of behaviors to avoid happens to name both halves of that problem: staying silent and interrupting. If you can assemble three candidates, run twenty minutes on a single published case as a group and have a fourth person tick those two boxes.

For the writing test there is nothing published to work from. What you can rehearse is the constraint: a fixed time, a fixed page count, and no chance to revise. Set forty minutes and one page against a case you have already worked, and read the result the next day.

What a mock case interview cannot do

It cannot reproduce the stakes. Nothing arranged between two people who like each other reproduces a decision about your next two years, and a candidate who is calm in mocks and rattled in the round has not failed at preparation.

It cannot tell you whether you would pass. No firm publishes a threshold or a scale, so a mock returns a diagnosis and never a verdict.

It cannot fix a dimension on its own. A mock surfaces which of the six dimensions is weakest and then the hour is over, and the repair happens in a drill the following day. A candidate who runs four mocks and no drills has an accurate and unchanging diagnosis.

It cannot supply cases indefinitely. Six published cases sit on McKinsey's and Bain's own sites, four and two, and BCG's thirteen modules sit on a third party's. After that, our case library is where the supply comes from, the case interview drills page covers the dimension-by-dimension work between mocks, and the method page sets out the six rubrics and their weights.

What changed on this mock interview page

We correct in public and we date the correction. The body above carries what the firms publish today.

5 October 2026. BCG publishes no case was false. The comparison table said "None" in the published cases column for BCG, and the closing section said six published cases exist across McKinsey and Bain. BCG announces OneDay@BCG from its own case interview preparation page, thirteen modules with 700,000+ participants, and the strategy module is a complete case in seven tasks on a named fictional client with downloadable statements and Model Answer blocks. The table row and the closing sentence now carry the figure and the nuance that goes with it: the content is written by BCG and it is served by a third party. Both halves are published together, because either one alone misleads.

5 October 2026. What the modules are not is now on the page. The firm never calls them case interviews, never says they resemble its selection case, prints "No grades · No assessments" and attaches a policy against listing the experience as work on a CV or a LinkedIn profile. A reader deciding whether to spend an evening on one needs all four of those, so they sit in the body rather than in this log.