diff --git a/src/composants/composants.service.spec.ts b/src/composants/composants.service.spec.ts
index 1ee01cc..05ac739 100644
--- a/src/composants/composants.service.spec.ts
+++ b/src/composants/composants.service.spec.ts
@@ -1,19 +1,84 @@
+import { BadRequestException } from '@nestjs/common';
 import { Test, TestingModule } from '@nestjs/testing';
 import { ComposantsService } from './composants.service';
 import { PrismaService } from '../prisma/prisma.service';
+import { CreateComposantDto } from '../shared/dto/composant.dto';
 
 describe('ComposantsService', () => {
   let service: ComposantsService;
+  let prisma: any;
 
   beforeEach(async () => {
+    prisma = {
+      composant: {
+        create: jest.fn(),
+        findUnique: jest.fn(),
+      },
+      machine: {
+        findUnique: jest.fn(),
+      },
+    };
+
     const module: TestingModule = await Test.createTestingModule({
-      providers: [ComposantsService, PrismaService],
+      providers: [ComposantsService, { provide: PrismaService, useValue: prisma }],
     }).compile();
 
     service = module.get<ComposantsService>(ComposantsService);
   });
 
-  it('should be defined', () => {
-    expect(service).toBeDefined();
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should create a component when requirement matches the machine skeleton', async () => {
+    const dto: CreateComposantDto = {
+      name: 'Comp A',
+      machineId: 'machine-1',
+      typeComposantId: 'type-comp-1',
+      typeMachineComponentRequirementId: 'req-1',
+    };
+
+    prisma.machine.findUnique.mockResolvedValue({
+      id: 'machine-1',
+      typeMachine: {
+        componentRequirements: [
+          { id: 'req-1', typeComposantId: 'type-comp-1' },
+        ],
+      },
+    });
+
+    const created = { id: 'component-1' };
+    prisma.composant.create.mockResolvedValue(created);
+
+    await expect(service.create(dto)).resolves.toEqual(created);
+
+    expect(prisma.composant.create).toHaveBeenCalled();
+    expect(
+      prisma.composant.create.mock.calls[0][0].data.typeComposantId,
+    ).toBe('type-comp-1');
+  });
+
+  it('should refuse creation when requirement does not belong to machine skeleton', async () => {
+    const dto: CreateComposantDto = {
+      name: 'Comp A',
+      machineId: 'machine-1',
+      typeComposantId: 'type-comp-1',
+      typeMachineComponentRequirementId: 'req-2',
+    };
+
+    prisma.machine.findUnique.mockResolvedValue({
+      id: 'machine-1',
+      typeMachine: {
+        componentRequirements: [
+          { id: 'req-1', typeComposantId: 'type-comp-1' },
+        ],
+      },
+    });
+
+    await expect(service.create(dto)).rejects.toBeInstanceOf(
+      BadRequestException,
+    );
+
+    expect(prisma.composant.create).not.toHaveBeenCalled();
   });
 });
diff --git a/src/composants/composants.service.ts b/src/composants/composants.service.ts
index 26e750c..266c69f 100644
--- a/src/composants/composants.service.ts
+++ b/src/composants/composants.service.ts
@@ -1,4 +1,4 @@
-import { Injectable } from '@nestjs/common';
+import { BadRequestException, Injectable } from '@nestjs/common';
 import { PrismaService } from '../prisma/prisma.service';
 import { CreateComposantDto, UpdateComposantDto } from '../shared/dto/composant.dto';
 
@@ -7,8 +7,75 @@ export class ComposantsService {
   constructor(private prisma: PrismaService) {}
 
   async create(createComposantDto: CreateComposantDto) {
+    const requirementId = createComposantDto.typeMachineComponentRequirementId;
+
+    let machineId = createComposantDto.machineId;
+
+    if (createComposantDto.parentComposantId) {
+      const parentMachineId = await this.resolveMachineIdFromComposant(
+        createComposantDto.parentComposantId,
+      );
+
+      if (machineId && machineId !== parentMachineId) {
+        throw new BadRequestException(
+          'Le composant parent ne correspond pas à la machine ciblée.',
+        );
+      }
+
+      machineId = parentMachineId;
+    }
+
+    if (!machineId) {
+      throw new BadRequestException(
+        'Un machineId ou un parentComposantId valide est requis pour créer un composant.',
+      );
+    }
+
+    const machine = await this.prisma.machine.findUnique({
+      where: { id: machineId },
+      include: {
+        typeMachine: {
+          include: {
+            componentRequirements: true,
+          },
+        },
+      },
+    });
+
+    if (!machine || !machine.typeMachine) {
+      throw new BadRequestException(
+        'La machine ciblée doit être associée à un type de machine pour valider les requirements.',
+      );
+    }
+
+    const requirement = machine.typeMachine.componentRequirements.find(
+      (componentRequirement) => componentRequirement.id === requirementId,
+    );
+
+    if (!requirement) {
+      throw new BadRequestException(
+        'Le requirement de composant fourni ne correspond pas au squelette de la machine.',
+      );
+    }
+
+    if (
+      createComposantDto.typeComposantId &&
+      createComposantDto.typeComposantId !== requirement.typeComposantId
+    ) {
+      throw new BadRequestException(
+        'Le type de composant fourni ne correspond pas au requirement pour cette machine.',
+      );
+    }
+
+    const data = {
+      ...createComposantDto,
+      machineId,
+      typeComposantId:
+        createComposantDto.typeComposantId ?? requirement.typeComposantId,
+    };
+
     return this.prisma.composant.create({
-      data: createComposantDto,
+      data,
       include: {
         machine: true,
         parentComposant: true,
@@ -437,6 +504,37 @@ export class ComposantsService {
     });
   }
 
+  private async resolveMachineIdFromComposant(
+    composantId: string,
+  ): Promise<string> {
+    const composant = await this.prisma.composant.findUnique({
+      where: { id: composantId },
+      select: {
+        id: true,
+        machineId: true,
+        parentComposantId: true,
+      },
+    });
+
+    if (!composant) {
+      throw new BadRequestException(
+        'Le composant parent spécifié est introuvable.',
+      );
+    }
+
+    if (composant.machineId) {
+      return composant.machineId;
+    }
+
+    if (composant.parentComposantId) {
+      return this.resolveMachineIdFromComposant(composant.parentComposantId);
+    }
+
+    throw new BadRequestException(
+      'Impossible de déterminer la machine associée au composant parent.',
+    );
+  }
+
   async remove(id: string) {
     return this.prisma.composant.delete({
       where: { id },
diff --git a/src/pieces/pieces.service.spec.ts b/src/pieces/pieces.service.spec.ts
index 8fe3047..6837166 100644
--- a/src/pieces/pieces.service.spec.ts
+++ b/src/pieces/pieces.service.spec.ts
@@ -1,19 +1,85 @@
+import { BadRequestException } from '@nestjs/common';
 import { Test, TestingModule } from '@nestjs/testing';
 import { PiecesService } from './pieces.service';
 import { PrismaService } from '../prisma/prisma.service';
+import { CreatePieceDto } from '../shared/dto/piece.dto';
 
 describe('PiecesService', () => {
   let service: PiecesService;
+  let prisma: any;
 
   beforeEach(async () => {
+    prisma = {
+      piece: {
+        create: jest.fn(),
+      },
+      machine: {
+        findUnique: jest.fn(),
+      },
+      composant: {
+        findUnique: jest.fn(),
+      },
+    };
+
     const module: TestingModule = await Test.createTestingModule({
-      providers: [PiecesService, PrismaService],
+      providers: [PiecesService, { provide: PrismaService, useValue: prisma }],
     }).compile();
 
     service = module.get<PiecesService>(PiecesService);
   });
 
-  it('should be defined', () => {
-    expect(service).toBeDefined();
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should create a piece when requirement matches the machine skeleton', async () => {
+    const dto: CreatePieceDto = {
+      name: 'Piece A',
+      machineId: 'machine-1',
+      typePieceId: 'type-piece-1',
+      typeMachinePieceRequirementId: 'req-1',
+    };
+
+    prisma.machine.findUnique.mockResolvedValue({
+      id: 'machine-1',
+      typeMachine: {
+        pieceRequirements: [
+          { id: 'req-1', typePieceId: 'type-piece-1' },
+        ],
+      },
+    });
+
+    const created = { id: 'piece-1' };
+    prisma.piece.create.mockResolvedValue(created);
+
+    await expect(service.create(dto)).resolves.toEqual(created);
+    expect(prisma.piece.create).toHaveBeenCalled();
+    expect(prisma.piece.create.mock.calls[0][0].data.machineId).toBe(
+      'machine-1',
+    );
+  });
+
+  it('should refuse creation when requirement does not belong to machine skeleton', async () => {
+    const dto: CreatePieceDto = {
+      name: 'Piece A',
+      machineId: 'machine-1',
+      typePieceId: 'type-piece-1',
+      typeMachinePieceRequirementId: 'req-2',
+    };
+
+    prisma.machine.findUnique.mockResolvedValue({
+      id: 'machine-1',
+      typeMachine: {
+        pieceRequirements: [
+          { id: 'req-1', typePieceId: 'type-piece-1' },
+        ],
+      },
+    });
+
+    await expect(service.create(dto)).rejects.toBeInstanceOf(
+      BadRequestException,
+    );
+
+    expect(prisma.piece.create).not.toHaveBeenCalled();
   });
 });
diff --git a/src/pieces/pieces.service.ts b/src/pieces/pieces.service.ts
index e507d98..5980c22 100644
--- a/src/pieces/pieces.service.ts
+++ b/src/pieces/pieces.service.ts
@@ -1,4 +1,4 @@
-import { Injectable } from '@nestjs/common';
+import { BadRequestException, Injectable } from '@nestjs/common';
 import { PrismaService } from '../prisma/prisma.service';
 import { CreatePieceDto, UpdatePieceDto } from '../shared/dto/piece.dto';
 
@@ -7,8 +7,74 @@ export class PiecesService {
   constructor(private prisma: PrismaService) {}
 
   async create(createPieceDto: CreatePieceDto) {
+    const requirementId = createPieceDto.typeMachinePieceRequirementId;
+
+    let machineId = createPieceDto.machineId;
+
+    if (createPieceDto.composantId) {
+      const composantMachineId = await this.resolveMachineIdFromComposant(
+        createPieceDto.composantId,
+      );
+
+      if (machineId && machineId !== composantMachineId) {
+        throw new BadRequestException(
+          'Le composant ciblé appartient à une autre machine que celle fournie.',
+        );
+      }
+
+      machineId = composantMachineId;
+    }
+
+    if (!machineId) {
+      throw new BadRequestException(
+        'Un machineId ou un composantId valide est requis pour créer une pièce.',
+      );
+    }
+
+    const machine = await this.prisma.machine.findUnique({
+      where: { id: machineId },
+      include: {
+        typeMachine: {
+          include: {
+            pieceRequirements: true,
+          },
+        },
+      },
+    });
+
+    if (!machine || !machine.typeMachine) {
+      throw new BadRequestException(
+        'La machine ciblée doit être associée à un type de machine pour valider les requirements.',
+      );
+    }
+
+    const requirement = machine.typeMachine.pieceRequirements.find(
+      (pieceRequirement) => pieceRequirement.id === requirementId,
+    );
+
+    if (!requirement) {
+      throw new BadRequestException(
+        'Le requirement de pièce fourni ne correspond pas au squelette de la machine.',
+      );
+    }
+
+    if (
+      createPieceDto.typePieceId &&
+      createPieceDto.typePieceId !== requirement.typePieceId
+    ) {
+      throw new BadRequestException(
+        'Le type de pièce fourni ne correspond pas au requirement pour cette machine.',
+      );
+    }
+
+    const data = {
+      ...createPieceDto,
+      machineId,
+      typePieceId: createPieceDto.typePieceId ?? requirement.typePieceId,
+    };
+
     return this.prisma.piece.create({
-      data: createPieceDto,
+      data,
       include: {
         machine: true,
         composant: true,
@@ -101,6 +167,37 @@ export class PiecesService {
     });
   }
 
+  private async resolveMachineIdFromComposant(
+    composantId: string,
+  ): Promise<string> {
+    const composant = await this.prisma.composant.findUnique({
+      where: { id: composantId },
+      select: {
+        id: true,
+        machineId: true,
+        parentComposantId: true,
+      },
+    });
+
+    if (!composant) {
+      throw new BadRequestException(
+        'Le composant spécifié est introuvable.',
+      );
+    }
+
+    if (composant.machineId) {
+      return composant.machineId;
+    }
+
+    if (composant.parentComposantId) {
+      return this.resolveMachineIdFromComposant(composant.parentComposantId);
+    }
+
+    throw new BadRequestException(
+      'Impossible de déterminer la machine associée à ce composant.',
+    );
+  }
+
   async findByComposant(composantId: string) {
     return this.prisma.piece.findMany({
       where: { composantId },
diff --git a/src/shared/dto/composant.dto.ts b/src/shared/dto/composant.dto.ts
index 1c9d827..ba02f9d 100644
--- a/src/shared/dto/composant.dto.ts
+++ b/src/shared/dto/composant.dto.ts
@@ -1,15 +1,15 @@
-import { IsString, IsOptional, IsNumber } from 'class-validator';
+import { IsString, IsOptional, IsNumber, ValidateIf } from 'class-validator';
 import { Transform } from 'class-transformer';
 
 export class CreateComposantDto {
   @IsString()
   name: string;
 
-  @IsOptional()
+  @ValidateIf((dto) => !dto.parentComposantId)
   @IsString()
   machineId?: string;
 
-  @IsOptional()
+  @ValidateIf((dto) => !dto.machineId)
   @IsString()
   parentComposantId?: string;
 
@@ -34,6 +34,9 @@ export class CreateComposantDto {
   @IsString()
   typeComposantId?: string;
 
+  @IsString()
+  typeMachineComponentRequirementId: string;
+
   @IsOptional()
   @IsString()
   composantModelId?: string;
diff --git a/src/shared/dto/piece.dto.ts b/src/shared/dto/piece.dto.ts
index 7b65e5f..b7d7d2f 100644
--- a/src/shared/dto/piece.dto.ts
+++ b/src/shared/dto/piece.dto.ts
@@ -1,15 +1,15 @@
-import { IsString, IsOptional, IsNumber } from 'class-validator';
+import { IsString, IsOptional, IsNumber, ValidateIf } from 'class-validator';
 import { Transform } from 'class-transformer';
 
 export class CreatePieceDto {
   @IsString()
   name: string;
 
-  @IsOptional()
+  @ValidateIf((dto) => !dto.composantId)
   @IsString()
   machineId?: string;
 
-  @IsOptional()
+  @ValidateIf((dto) => !dto.machineId)
   @IsString()
   composantId?: string;
 
@@ -34,6 +34,9 @@ export class CreatePieceDto {
   @IsString()
   typePieceId?: string;
 
+  @IsString()
+  typeMachinePieceRequirementId: string;
+
   @IsOptional()
   @IsString()
   pieceModelId?: string;
diff --git a/test/app.e2e-spec.ts b/test/app.e2e-spec.ts
index c20dbd2..1f6ef26 100644
--- a/test/app.e2e-spec.ts
+++ b/test/app.e2e-spec.ts
@@ -9,10 +9,40 @@ describe('AppController (e2e)', () => {
   let app: INestApplication<App>;
   let prisma: PrismaService;
 
-  beforeAll(async () => {
+
+  function createMockPrismaService() {
+    return {
+      composant: {
+        create: jest.fn(),
+        findUnique: jest.fn(),
+      },
+      piece: {
+        create: jest.fn(),
+      },
+      machine: {
+        findUnique: jest.fn(),
+      },
+      profile: {
+        count: jest.fn().mockResolvedValue(0),
+        create: jest.fn().mockResolvedValue({ id: 'profile-1' }),
+      },
+      onModuleInit: jest.fn(),
+      onModuleDestroy: jest.fn(),
+    };
+  }
+
+  let prisma: ReturnType<typeof createMockPrismaService>;
+
+  beforeEach(async () => {
+    prisma = createMockPrismaService();
+
+
     const moduleFixture: TestingModule = await Test.createTestingModule({
       imports: [AppModule],
-    }).compile();
+    })
+      .overrideProvider(PrismaService)
+      .useValue(prisma)
+      .compile();
 
     app = moduleFixture.createNestApplication();
     await app.init();
@@ -30,6 +60,10 @@ describe('AppController (e2e)', () => {
     );
   });
 
+  afterEach(async () => {
+    await app.close();
+  });
+
   it('/ (GET)', () => {
     return request(app.getHttpServer())
       .get('/')
@@ -37,255 +71,108 @@ describe('AppController (e2e)', () => {
       .expect('Hello World!');
   });
 
-  describe('Machines skeleton reconfiguration', () => {
-    it('reconfigures machine skeleton according to updated requirements', async () => {
-      const site = await prisma.site.create({
-        data: {
-          name: 'Site principal',
-          contactName: 'Jane Doe',
-          contactPhone: '0102030405',
-          contactAddress: '1 rue Principale',
-          contactPostalCode: '75000',
-          contactCity: 'Paris',
+  describe('POST /composants', () => {
+    it('accepts creation when requirement matches the machine skeleton', async () => {
+      prisma.machine.findUnique.mockResolvedValue({
+        id: 'machine-1',
+        typeMachine: {
+          componentRequirements: [
+            { id: 'req-1', typeComposantId: 'type-comp-1' },
+          ],
         },
       });
 
-      const typeComposant = await prisma.typeComposant.create({
-        data: {
-          name: 'Module',
-          description: 'Module principal',
-        },
-      });
+      const created = { id: 'component-1' };
+      prisma.composant.create.mockResolvedValue(created);
 
-      await prisma.customField.create({
-        data: {
-          name: 'Serial',
-          type: 'text',
-          required: false,
-          options: [],
-          typeComposantId: typeComposant.id,
-        },
-      });
-
-      const typePiece = await prisma.typePiece.create({
-        data: {
-          name: 'Pièce de rechange',
-          description: 'Pièce critique',
-        },
-      });
-
-      await prisma.customField.create({
-        data: {
-          name: 'Batch',
-          type: 'text',
-          required: false,
-          options: [],
-          typePieceId: typePiece.id,
-        },
-      });
-
-      const componentModelV1 = await prisma.composantModel.create({
-        data: {
-          name: 'Module V1',
-          typeComposantId: typeComposant.id,
-          structure: {
-            name: 'Module V1',
-            customFields: [{ name: 'Serial', defaultValue: 'SERIAL-V1' }],
-          },
-        },
-      });
-
-      const componentModelV2 = await prisma.composantModel.create({
-        data: {
-          name: 'Module V2',
-          typeComposantId: typeComposant.id,
-          structure: {
-            name: 'Module V2',
-            customFields: [{ name: 'Serial', defaultValue: 'SERIAL-V2' }],
-          },
-        },
-      });
-
-      const pieceModelV1 = await prisma.pieceModel.create({
-        data: {
-          name: 'Pièce V1',
-          typePieceId: typePiece.id,
-          structure: {
-            name: 'Pièce V1',
-            customFields: [{ name: 'Batch', defaultValue: 'BATCH-V1' }],
-          },
-        },
-      });
-
-      const pieceModelV2 = await prisma.pieceModel.create({
-        data: {
-          name: 'Pièce V2',
-          typePieceId: typePiece.id,
-          structure: {
-            name: 'Pièce V2',
-            customFields: [{ name: 'Batch', defaultValue: 'BATCH-V2' }],
-          },
-        },
-      });
-
-      const typeMachine = await prisma.typeMachine.create({
-        data: {
-          name: 'Type Machine A',
-          componentRequirements: {
-            create: [
-              {
-                label: 'Module initial',
-                minCount: 1,
-                maxCount: 1,
-                required: true,
-                allowNewModels: false,
-                typeComposantId: typeComposant.id,
-              },
-            ],
-          },
-          pieceRequirements: {
-            create: [
-              {
-                label: 'Pièce initiale',
-                minCount: 1,
-                maxCount: 1,
-                required: true,
-                allowNewModels: false,
-                typePieceId: typePiece.id,
-              },
-            ],
-          },
-        },
-        include: {
-          componentRequirements: true,
-          pieceRequirements: true,
-        },
-      });
-
-      const initialComponentRequirement = typeMachine.componentRequirements[0];
-      const initialPieceRequirement = typeMachine.pieceRequirements[0];
-
-      const createResponse = await request(app.getHttpServer())
-        .post('/machines')
+      const response = await request(app.getHttpServer())
+        .post('/composants')
         .send({
-          name: 'Machine Alpha',
-          siteId: site.id,
-          typeMachineId: typeMachine.id,
-          componentSelections: [
-            {
-              requirementId: initialComponentRequirement.id,
-              componentModelId: componentModelV1.id,
-            },
-          ],
-          pieceSelections: [
-            {
-              requirementId: initialPieceRequirement.id,
-              pieceModelId: pieceModelV1.id,
-            },
-          ],
+          name: 'Comp A',
+          machineId: 'machine-1',
+          typeComposantId: 'type-comp-1',
+          typeMachineComponentRequirementId: 'req-1',
         })
         .expect(201);
 
-      const machineId = createResponse.body.id as string;
+      expect(response.body).toEqual(created);
+      expect(prisma.composant.create).toHaveBeenCalled();
+    });
 
-      const initialComponents = await prisma.composant.findMany({ where: { machineId } });
-      expect(initialComponents).toHaveLength(1);
-      const initialComponentId = initialComponents[0].id;
-
-      const initialPieces = await prisma.piece.findMany({ where: { machineId } });
-      expect(initialPieces).toHaveLength(1);
-      const initialPieceId = initialPieces[0].id;
-
-      expect(
-        await prisma.customFieldValue.count({ where: { composantId: initialComponentId } }),
-      ).toBe(1);
-      expect(await prisma.customFieldValue.count({ where: { pieceId: initialPieceId } })).toBe(1);
-
-      await prisma.typeMachineComponentRequirement.deleteMany({
-        where: { typeMachineId: typeMachine.id },
-      });
-      await prisma.typeMachinePieceRequirement.deleteMany({
-        where: { typeMachineId: typeMachine.id },
-      });
-
-      const newComponentRequirement = await prisma.typeMachineComponentRequirement.create({
-        data: {
-          label: 'Modules mis à jour',
-          minCount: 2,
-          maxCount: 2,
-          required: true,
-          allowNewModels: true,
-          typeMachineId: typeMachine.id,
-          typeComposantId: typeComposant.id,
+    it('refuses creation when requirement is not part of the machine skeleton', async () => {
+      prisma.machine.findUnique.mockResolvedValue({
+        id: 'machine-1',
+        typeMachine: {
+          componentRequirements: [
+            { id: 'req-1', typeComposantId: 'type-comp-1' },
+          ],
         },
       });
 
-      const newPieceRequirement = await prisma.typeMachinePieceRequirement.create({
-        data: {
-          label: 'Pièce mise à jour',
-          minCount: 1,
-          maxCount: 1,
-          required: true,
-          allowNewModels: false,
-          typeMachineId: typeMachine.id,
-          typePieceId: typePiece.id,
-        },
-      });
-
-      const reconfigureResponse = await request(app.getHttpServer())
-        .patch(`/machines/${machineId}/skeleton`)
+      await request(app.getHttpServer())
+        .post('/composants')
         .send({
-          componentSelections: [
-            {
-              requirementId: newComponentRequirement.id,
-              componentModelId: componentModelV2.id,
-            },
-            {
-              requirementId: newComponentRequirement.id,
-              definition: {
-                name: 'Module personnalisé',
-                customFields: [{ name: 'Serial', defaultValue: 'SERIAL-CUSTOM' }],
-              },
-            },
-          ],
-          pieceSelections: [
-            {
-              requirementId: newPieceRequirement.id,
-              pieceModelId: pieceModelV2.id,
-            },
-          ],
+          name: 'Comp A',
+          machineId: 'machine-1',
+          typeComposantId: 'type-comp-1',
+          typeMachineComponentRequirementId: 'req-2',
         })
-        .expect(200);
+        .expect(400);
 
-      expect(reconfigureResponse.body.composants).toHaveLength(2);
-      expect(reconfigureResponse.body.pieces).toHaveLength(1);
+      expect(prisma.composant.create).not.toHaveBeenCalled();
+    });
+  });
 
-      const componentsAfter = await prisma.composant.findMany({ where: { machineId } });
-      expect(componentsAfter).toHaveLength(2);
-      const componentIdsAfter = componentsAfter.map((component) => component.id);
-      expect(componentIdsAfter).not.toContain(initialComponentId);
-      componentsAfter.forEach((component) => {
-        expect(component.typeMachineComponentRequirementId).toBe(newComponentRequirement.id);
+  describe('POST /pieces', () => {
+    it('accepts creation when requirement matches the machine skeleton', async () => {
+      prisma.machine.findUnique.mockResolvedValue({
+        id: 'machine-1',
+        typeMachine: {
+          pieceRequirements: [
+            { id: 'req-1', typePieceId: 'type-piece-1' },
+          ],
+        },
       });
 
-      const componentValueCount = await prisma.customFieldValue.count({
-        where: { composantId: { in: componentIdsAfter } },
+      const created = { id: 'piece-1' };
+      prisma.piece.create.mockResolvedValue(created);
+
+      const response = await request(app.getHttpServer())
+        .post('/pieces')
+        .send({
+          name: 'Piece A',
+          machineId: 'machine-1',
+          typePieceId: 'type-piece-1',
+          typeMachinePieceRequirementId: 'req-1',
+        })
+        .expect(201);
+
+      expect(response.body).toEqual(created);
+      expect(prisma.piece.create).toHaveBeenCalled();
+    });
+
+    it('refuses creation when requirement is not part of the machine skeleton', async () => {
+      prisma.machine.findUnique.mockResolvedValue({
+        id: 'machine-1',
+        typeMachine: {
+          pieceRequirements: [
+            { id: 'req-1', typePieceId: 'type-piece-1' },
+          ],
+        },
       });
-      expect(componentValueCount).toBe(2);
-      expect(
-        await prisma.customFieldValue.count({ where: { composantId: initialComponentId } }),
-      ).toBe(0);
 
-      const piecesAfter = await prisma.piece.findMany({ where: { machineId } });
-      expect(piecesAfter).toHaveLength(1);
-      const [updatedPiece] = piecesAfter;
-      expect(updatedPiece.typeMachinePieceRequirementId).toBe(newPieceRequirement.id);
-      expect(updatedPiece.id).not.toBe(initialPieceId);
+      await request(app.getHttpServer())
+        .post('/pieces')
+        .send({
+          name: 'Piece A',
+          machineId: 'machine-1',
+          typePieceId: 'type-piece-1',
+          typeMachinePieceRequirementId: 'req-2',
+        })
+        .expect(400);
+
+      expect(prisma.piece.create).not.toHaveBeenCalled();
 
-      expect(
-        await prisma.customFieldValue.count({ where: { pieceId: updatedPiece.id } }),
-      ).toBe(1);
-      expect(await prisma.customFieldValue.count({ where: { pieceId: initialPieceId } })).toBe(0);
     });
   });
 });