Functional and REST Testing
- Postman and Newman for API test collections and CI integration
- REST Assured for Java-based API test suites
- SoapUI for legacy SOAP and complex enterprise APIs
API Testing Services
Digisoft Solution provides api testing services covering functional, contract, performance, and security testing, delivered by engineers who build APIs, not a QA vendor testing endpoints from the outside. Our api testing company background means we understand what actually breaks integrations, not just what a functional test suite checks.
100% Confidential
NDA-Protected
700+Projects Delivered
100+Tech Professionals
13+Years Experience
13Industries Served
98%Client Retention
Talk to an API Testing Specialist
Tell us what your API does and who consumes it. We will tell you honestly what testing scope you actually need.
Social Proof Bar
Coverage Gaps
The API Failures That Slip Past Standard Testing
Functional, performance, and security testing catch most problems. A specific set of failures keeps slipping through even well-tested APIs, because most api testing service providers do not test for them at all.
What standard API testing usually misses:
- Breaking changes that only surface when a consumer calls the new version. Your functional tests pass because they test the current contract, not whether the previous contract still holds for existing integration partners.
- Contract mismatches between services that only appear in production. Service A assumes a field is always present, Service B occasionally omits it, and nothing catches this until real traffic hits the gap.
- Webhook and event delivery failures. Most testing focuses on request-response APIs and skips webhook retry logic, delivery ordering, and duplicate event handling entirely.
- Protocol-specific issues treated generically. GraphQL over-fetching and query complexity abuse, gRPC streaming edge cases, and REST versioning each need a different testing approach, not one generic checklist applied to all of them.
These are not exotic edge cases. They are the specific class of failure that causes integration partners to lose trust in your API, which is a harder problem to fix than a functional bug.
Find Out What Your API Testing Is Currently Missing
Send us your API documentation or current test coverage. We identify gaps against the list above within 48 hours, no cost, no obligation.
Services
Our API Testing Services
Functional API Testing
We verify every endpoint behaves correctly against its specification: correct status codes, response payloads, and error handling for both valid and invalid requests.
- Request and response validation against API specifications
- Positive, negative, and boundary condition testing
- Error handling and status code verification
- Data integrity checks across create, read, update, and delete operations
REST API Testing Services
Our rest api testing services address the specific concerns REST APIs introduce: resource modeling, HTTP method semantics, and versioning strategy.
- HTTP method and status code correctness (idempotency of PUT/DELETE, proper use of PATCH)
- Resource relationship and nested endpoint testing
- Pagination, filtering, and sorting parameter validation
- HATEOAS and hypermedia link validation where applicable
GraphQL API Testing Services
GraphQL introduces failure modes REST does not have. Our graphql api testing services address query complexity, schema evolution, and the specific ways GraphQL APIs get abused or misused.
- Schema validation and breaking change detection
- Query complexity and depth limit testing to prevent resource exhaustion
- Over-fetching and under-fetching behavior validation
- Resolver-level testing for N+1 query and performance issues
API Contract Testing
Contract testing is the gap most API testing skips entirely. Instead of testing an API in isolation, we validate that the contract between a service and its consumers, request format, response schema, required fields, stays honored as both sides evolve independently.
- Consumer-driven contract testing between microservices
- Schema validation against OpenAPI, GraphQL SDL, or Protobuf definitions
- Breaking change detection before deployment, not after
- Contract test integration into CI/CD so both provider and consumer teams get early warning
API Versioning and Backward Compatibility Testing
APIs change. The question is whether existing integrations survive that change. We test new versions against the assumptions your existing consumers actually depend on, not just the documented contract.
- Backward compatibility testing across API version boundaries
- Deprecation path validation for sunset endpoints
- Consumer impact analysis before breaking changes ship
- Version negotiation and content-type handling testing
Webhook and Event-Driven API Testing
Webhooks fail differently than request-response APIs: delivery can be delayed, retried, duplicated, or arrive out of order. Most testing ignores this entirely.
- Webhook delivery and retry logic testing
- Duplicate event and idempotency handling validation
- Event ordering and out-of-sequence delivery testing
- Signature verification and payload integrity testing
API Security Testing Services
Our api security testing services cover authentication, authorization, and injection testing at the API layer. For deeper penetration testing and compliance-driven security assessment, see our full Security Testing Services page.
- Authentication and authorization boundary testing
- Rate limiting and abuse prevention validation
- Input validation and injection testing at API endpoints
- API key and token exposure checks
API Performance Testing Services
Our api performance testing services measure response time and throughput under normal and elevated conditions, so slow endpoints get found before they become a customer complaint.
- Response time benchmarking across endpoints
- Database query performance analysis for data-heavy endpoints
- Third-party dependency latency impact testing
- Performance regression tracking across releases
API Load Testing Services
Our api load testing services simulate realistic and peak concurrent request volume to find your API's actual breaking point before real traffic finds it.
- Concurrent request load simulation at expected and peak volumes
- Rate limit and throttling behavior validation under load
- Stress testing to identify the point of failure
- Scalability recommendations based on load test results
API Test Automation Services
Our api test automation services and automated api testing services build suites that run on every deployment, catching regressions and contract breaks before they reach consumers.
- Automated functional and contract test suites integrated into CI/CD
- Data-driven testing to cover multiple scenarios per endpoint
- Automated schema and breaking change detection on every build
Functional API Testing
We verify every endpoint behaves correctly against its specification: correct status codes, response payloads, and error handling for both valid and invalid requests.
- Request and response validation against API specifications
- Positive, negative, and boundary condition testing
- Error handling and status code verification
- Data integrity checks across create, read, update, and delete operations
REST API Testing Services
Our rest api testing services address the specific concerns REST APIs introduce: resource modeling, HTTP method semantics, and versioning strategy.
- HTTP method and status code correctness (idempotency of PUT/DELETE, proper use of PATCH)
- Resource relationship and nested endpoint testing
- Pagination, filtering, and sorting parameter validation
- HATEOAS and hypermedia link validation where applicable
GraphQL API Testing Services
GraphQL introduces failure modes REST does not have. Our graphql api testing services address query complexity, schema evolution, and the specific ways GraphQL APIs get abused or misused.
- Schema validation and breaking change detection
- Query complexity and depth limit testing to prevent resource exhaustion
- Over-fetching and under-fetching behavior validation
- Resolver-level testing for N+1 query and performance issues
API Contract Testing
Contract testing is the gap most API testing skips entirely. Instead of testing an API in isolation, we validate that the contract between a service and its consumers, request format, response schema, required fields, stays honored as both sides evolve independently.
- Consumer-driven contract testing between microservices
- Schema validation against OpenAPI, GraphQL SDL, or Protobuf definitions
- Breaking change detection before deployment, not after
- Contract test integration into CI/CD so both provider and consumer teams get early warning
API Versioning and Backward Compatibility Testing
APIs change. The question is whether existing integrations survive that change. We test new versions against the assumptions your existing consumers actually depend on, not just the documented contract.
- Backward compatibility testing across API version boundaries
- Deprecation path validation for sunset endpoints
- Consumer impact analysis before breaking changes ship
- Version negotiation and content-type handling testing
Webhook and Event-Driven API Testing
Webhooks fail differently than request-response APIs: delivery can be delayed, retried, duplicated, or arrive out of order. Most testing ignores this entirely.
- Webhook delivery and retry logic testing
- Duplicate event and idempotency handling validation
- Event ordering and out-of-sequence delivery testing
- Signature verification and payload integrity testing
API Security Testing Services
Our api security testing services cover authentication, authorization, and injection testing at the API layer. For deeper penetration testing and compliance-driven security assessment, see our full Security Testing Services page.
- Authentication and authorization boundary testing
- Rate limiting and abuse prevention validation
- Input validation and injection testing at API endpoints
- API key and token exposure checks
API Performance Testing Services
Our api performance testing services measure response time and throughput under normal and elevated conditions, so slow endpoints get found before they become a customer complaint.
- Response time benchmarking across endpoints
- Database query performance analysis for data-heavy endpoints
- Third-party dependency latency impact testing
- Performance regression tracking across releases
API Load Testing Services
Our api load testing services simulate realistic and peak concurrent request volume to find your API's actual breaking point before real traffic finds it.
- Concurrent request load simulation at expected and peak volumes
- Rate limit and throttling behavior validation under load
- Stress testing to identify the point of failure
- Scalability recommendations based on load test results
API Test Automation Services
Our api test automation services and automated api testing services build suites that run on every deployment, catching regressions and contract breaks before they reach consumers.
- Automated functional and contract test suites integrated into CI/CD
- Data-driven testing to cover multiple scenarios per endpoint
- Automated schema and breaking change detection on every build
Tell us what your API does and who consumes it. We will tell you honestly what testing scope you actually need.
Schedule a Quick CallTools
API Testing Tools We Use
We select api testing tools based on your API's protocol and your team's existing stack, not a single default.
GraphQL Testing
- Apollo Studio for schema validation and monitoring
- GraphQL Inspector for breaking change detection
Contract Testing
- Pact for consumer-driven contract testing
- Spectral for OpenAPI schema linting and validation
gRPC and Streaming APIs
- grpcurl and ghz for gRPC testing and load simulation
Performance and Load Testing
- JMeter and k6 for load and performance testing
- Gatling for high-throughput load scenarios
Security Testing
- Burp Suite and OWASP ZAP for API vulnerability scanning
Process
Our API Testing Process
Step 1: API Discovery and Risk Assessment (2-3 days)
We review your API documentation, consumer list, and protocol type to identify which risk areas above matter most for your specific API.
Step 2: Test Plan and Contract Definition (3-5 days)
We design test cases covering functional behavior, and where applicable, define or validate the contract your API commits to for its consumers.
Step 3: Functional and Contract Test Execution (Ongoing)
We execute functional, contract, and protocol-specific tests, logging defects and contract violations with reproduction details in real time.
Step 4: Performance and Load Testing (3-5 days)
We benchmark response times and simulate concurrent load to identify performance limits before real traffic finds them.
Step 5: Security Testing (3-5 days, or full engagement via Security Testing Services)
We test authentication, authorization, and input validation at the API layer, with deeper penetration testing available as a dedicated engagement.
Step 6: Automation Buildout and CI/CD Integration
We build automated regression and contract test suites integrated into your pipeline, so future changes get validated automatically, not manually re-checked every release.
See a Sample API Test Report
Ask us for an example contract test suite, load test summary, and defect report from a past engagement so you can evaluate our documentation standard.
Industries
Industry-Specific API Testing
Healthcare API Testing
We test HL7 and FHIR-based healthcare data exchange APIs, with attention to schema compliance and HIPAA-aware handling of test data.
Banking and FinTech API Testing
We prioritize contract testing and versioning validation for payment and transaction APIs, where a breaking change reaching a partner integration carries direct financial consequences.
Retail and Ecommerce API Testing
We prioritize webhook testing for payment and order status events, and load testing for inventory and checkout APIs during peak traffic.
Logistics and Manufacturing API Testing
We prioritize contract testing between tracking, inventory, and production system APIs, where a schema mismatch can affect physical operations, not just a dashboard.
Logistics Software Development | Manufacturing Software Development
Case Studies
Case Studies
A sample of API testing engagements and the measurable outcomes they produced.
Catching a Breaking Schema Change Before It Reached Partners
Challenge
A peace and governance intelligence platform aggregating data through multiple third-party APIs had no contract testing in place, leaving it vulnerable to silent breaking changes whenever an upstream data provider updated their API.
Result
We implemented consumer-driven contract testing across all data ingestion endpoints. This caught a field type change from an upstream provider in staging, before it reached production and silently corrupted downstream analysis, which manual QA had missed in prior releases.
60%
admin time reduction
8,000+
records migrated
99.95%
uptime maintained
Zero
compliance incidents
Fixing a Duplicate Payment Webhook Race Condition
Challenge
A grooming services marketplace processing payments through webhook notifications had an intermittent issue where a small number of transactions appeared to charge customers twice, but the cause was not reproducible through standard functional testing.
Result
Our webhook and event-driven testing identified a race condition in duplicate event handling during high-traffic periods. The fix added proper idempotency handling, and the duplicate charge issue did not recur in subsequent peak traffic events.
42%
faster instability detection
48hr to real time
reporting lag eliminated
12+
data sources unified
100%
public sector security met
Validating Backward Compatibility Before an API Version Upgrade
Challenge
A healthcare provider credentialing platform needed to upgrade its public API to support new functionality, but had several external integration partners depending on the existing version with no formal record of what those integrations relied on.
Result
We built backward compatibility tests based on actual historical API usage patterns from partner traffic logs, identifying two assumptions the new version would have broken. Both were addressed before the version upgrade shipped, and no partner integrations broke post-launch.
4.8★
app store rating
Significant
self service increase
Reduced
call centre load
Secure
authentication architecture
Testimonials
What Clients Say About Our API Testing
“Contract testing caught a change from a partner API before it silently broke our data pipeline. We would not have caught that with our old regression suite.”
“The duplicate charge issue had been intermittent and hard to reproduce for weeks. They found the actual race condition in the webhook handling within days.”
“They tested against how our partners actually used the API, not just what our documentation said. That is the difference that mattered before our version upgrade.”
Why Digisoft Solution
Why Teams Choose Digisoft Solution as Their API Testing Company
1
Engineers Who Build APIs, Not Just Test Them From Outside
Because our API testers sit inside the same 100+ person delivery organization that builds APIs end to end, they understand service architecture, contract design, and integration patterns, not just how to send requests and check responses.
2
We Test the Failures That Actually Cause Incidents
Contract mismatches, breaking changes, and webhook failures cause more real production incidents than missed functional bugs. We test for them specifically instead of treating API testing as a generic checklist.
3
Protocol-Aware Testing, Not One Approach for Everything
REST, GraphQL, gRPC, and webhook-based APIs each fail differently. We adjust our approach to the protocol instead of running the same generic test plan against all of them.
4
13+ Years and 700+ Projects of Pattern Recognition
Experience testing hundreds of real API integrations means we recognize the specific failure patterns in contract drift, versioning, and event handling before they become incidents.
Engagement
How to Engage Our API Testing Team
One-Time API Testing Engagement
A focused engagement to test a specific API or set of endpoints before a launch or major integration.
Ongoing Contract and Regression Testing
Continuous contract and regression testing integrated into your CI/CD pipeline, so every deployment gets validated automatically.
Dedicated API QA Team
A dedicated team of API testers embedded in your development process for organizations with continuous, high-volume API changes.
API Testing Staff Augmentation
Add individual API testing specialists to your existing QA team for a defined period or ongoing capacity.
Whether you need a one-time testing push before a major integration or ongoing contract and regression testing in your pipeline, our team starts with an honest coverage review.
Book Your Free Review NowFrequently Asked Questions
API testing services include functional, contract, performance, load, and security testing, scoped to your API's protocol and consumer base. Depending on your architecture, this may also include versioning and webhook-specific testing.
Contract testing validates that the agreement between an API and its consumers, request format, response schema, required fields, stays honored as both sides change independently. It matters because functional tests only verify current behavior, not whether a change breaks an assumption a consumer is relying on.
Yes. REST and GraphQL fail differently, so we scope testing to the protocol. REST testing focuses on resource modeling and versioning, while graphql api testing services focus on schema evolution, query complexity, and resolver-level performance.
API security testing as part of this page covers authentication, authorization, and input validation at the API layer as part of a broader testing engagement. For dedicated penetration testing, compliance-driven security assessment, and ongoing security testing as a service, see our full Security Testing Services page.
Yes. Webhook and event-driven testing covers delivery retry logic, duplicate event handling, and out-of-order delivery, failure modes that standard request-response API testing does not address at all.
Yes. Our automated api testing services and api test automation services integrate functional, contract, and regression testing into your pipeline, so tests run automatically on every deployment.
A focused functional and contract testing engagement typically takes one to two weeks. Adding load and security testing extends this by one to two weeks depending on API complexity. Ongoing contract and regression testing runs continuously alongside your release cycle.
Find Out What Your API Testing Is Actually Missing
Whether you need a one-time testing push before a major integration or ongoing contract and regression testing in your pipeline, our team starts with an honest coverage review.
Schedule Your Free API Coverage Review
Send your API documentation and current test coverage. We identify gaps within 48 hours.
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