> ## Documentation Index > Fetch the complete documentation index at: https://apidoc.mailercloud.com/llms.txt > Use this file to discover all available pages before exploring further. # Start a placement test > Sends a draft campaign to seed mailboxes at the chosen providers and reports where it lands (inbox, Gmail tabs, spam, missing). Each test uses one test from your Advanced Inbox Tracker allowance. Only draft regular campaigns with a subject, sender and content can be tested. Only one test can run per campaign at a time. If the draft has not changed since its last test, set `confirm_unchanged` to `true` to spend another test. Poll Get a placement test until `status` is no longer `running`; `eta_at` gives the expected finish time. ## OpenAPI ````yaml /openapi-v1.json post /v2/placement/tests openapi: 3.1.0 info: title: Mailercloud Marketing API version: 1.0.0 description: >- Campaigns, contacts, lists, segments, automations, and webhooks for the Mailercloud Marketing Platform. servers: - url: https://cloudapi.mailercloud.com/v1 security: - apiKey: [] tags: - name: Campaigns - name: Contacts - name: Lists - name: Tags - name: Segments - name: Custom Properties - name: Senders - name: Domains - name: Templates - name: Automations - name: Webhooks - name: Webforms - name: Inbox Tracker - name: Account paths: /v2/placement/tests: post: tags: - Inbox Tracker summary: Start a placement test description: >- Sends a draft campaign to seed mailboxes at the chosen providers and reports where it lands (inbox, Gmail tabs, spam, missing). Each test uses one test from your Advanced Inbox Tracker allowance. Only draft regular campaigns with a subject, sender and content can be tested. Only one test can run per campaign at a time. If the draft has not changed since its last test, set `confirm_unchanged` to `true` to spend another test. Poll Get a placement test until `status` is no longer `running`; `eta_at` gives the expected finish time. operationId: placement-start-test parameters: - name: Content-Type in: header required: true description: Request body type schema: type: string default: application/json requestBody: required: true content: application/json: schema: type: object required: - campaign_id - provider_ids properties: campaign_id: type: string description: Draft campaign id, as returned by the Campaigns API. provider_ids: type: array minItems: 1 maxItems: 100 items: type: string description: Provider ids from List placement providers. confirm_unchanged: type: boolean default: false description: >- Run again even though the draft has not changed since its last test. examples: Example-1: value: campaign_id: Hws provider_ids: - '1' - '2' responses: '201': description: Test started. content: application/json: schema: type: object properties: data: type: object properties: test_id: type: string status: type: string enum: - running started_at: type: string format: date-time seeds_total: type: integer tests_left: type: integer description: Tests left in the current period after this one. eta_at: type: - string - 'null' format: date-time description: >- Estimated finish time while the test is running; `null` otherwise. eta_seconds: type: - integer - 'null' description: >- Estimated seconds from start to finish while running; `null` otherwise. '400': description: Invalid body, or `provider_ids` empty, over 100 or unknown. content: application/json: schema: type: object properties: error: type: string description: Human-readable message. code: type: string enum: - INVALID_INPUT '401': description: Missing or invalid API key. '403': description: >- The account has no active Advanced Inbox Tracker add-on on a paid plan. content: application/json: schema: type: object properties: error: type: string description: Human-readable message. code: type: string enum: - ADDON_INACTIVE '404': description: Campaign not found for this account. content: application/json: schema: type: object properties: error: type: string description: Human-readable message. code: type: string enum: - CAMPAIGN_NOT_FOUND '409': description: >- The test cannot start: the campaign is not a draft regular campaign, the draft is incomplete, no tests are left, a test is already running, or the draft is unchanged. content: application/json: schema: type: object properties: error: type: string description: Human-readable message. code: type: string enum: - CAMPAIGN_TYPE_UNSUPPORTED - DRAFT_NOT_READY - QUOTA_EXHAUSTED - TEST_ALREADY_RUNNING - DRAFT_UNCHANGED resets_on: type: string description: 'With `QUOTA_EXHAUSTED`: when the allowance resets.' test_id: type: string description: 'With `TEST_ALREADY_RUNNING`: the running test.' '503': description: Placement testing is not available right now. Nothing was charged. content: application/json: schema: type: object properties: error: type: string description: Human-readable message. code: type: string enum: - PLACEMENT_UNAVAILABLE servers: - url: https://cloudapi.mailercloud.com components: securitySchemes: apiKey: type: apiKey in: header name: Authorization description: >- Your Mailercloud API key (plain text, no Bearer prefix). Create keys in Settings → API. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.