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Use a TestNG @DataProvider method to supply multiple argument sets to one @Test method. Each row of the provider’s returned data becomes a separate test invocation, and the values in that row are passed to the test method’s parameters in order.
How a TestNG DataProvider works
A provider is a method annotated with @DataProvider. A test connects to it by naming it in @Test(dataProvider = "..."). In the basic form shown in the TestNG documentation, the provider returns an Object[][]: each inner array is one invocation’s arguments.
For example, the first row below calls the test with "alice" and "correct-horse"; the second row calls it with "bob" and "battery-staple". The test method’s parameter count and types should match the values supplied by each row.
Basic example
Place the provider and test in the same class when the data is specific to that test or class:
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import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
public class LoginTest {
@DataProvider(name = "credentials")
public Object[][] credentials() {
return new Object[][] {
{"alice", "correct-horse"},
{"bob", "battery-staple"}
};
}
@Test(dataProvider = "credentials")
public void loginAcceptsCredentials(String username, String password) {
// Exercise the behavior under test here.
}
}This example illustrates the TestNG mechanism; it does not implement a login operation or make an assertion. Replace the comment with the behavior and assertions your test needs. The example uses Object[][], a documented form, not a claim that it is the only return form accepted by every TestNG version.
Put reusable data in another class
To share a provider across test classes, specify its class with dataProviderClass. The TestNG documentation says the provider method in that specified class needs to be static.
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import org.testng.annotations.DataProvider;
public class CommonTestData {
@DataProvider(name = "credentials")
public static Object[][] credentials() {
return new Object[][] {
{"alice", "correct-horse"},
{"bob", "battery-staple"}
};
}
}import org.testng.annotations.Test;
public class LoginTest {
@Test(dataProvider = "credentials", dataProviderClass = CommonTestData.class)
public void loginAcceptsCredentials(String username, String password) {
// Exercise the behavior under test here.
}
}Without dataProviderClass, TestNG looks for the named provider in the test class or a base class. Keeping a provider close to one consumer makes its purpose easy to see; placing it in a separate class can reduce duplication when multiple tests genuinely need the same inputs.
Reuse one provider for different test methods
A provider may accept java.lang.reflect.Method. TestNG supplies the method that is about to receive data, so the provider can select rows based on the requesting test method. This is useful when a shared provider serves tests that need different inputs; keep the selection logic explicit so a change to a test method name does not silently select the wrong data.
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import java.lang.reflect.Method;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
public class SharedDataTest {
@DataProvider(name = "cases")
public Object[][] cases(Method testMethod) {
if (testMethod.getName().equals("acceptsValidInput")) {
return new Object[][] {{"valid"}};
}
if (testMethod.getName().equals("rejectsInvalidInput")) {
return new Object[][] {{"invalid"}};
}
throw new IllegalArgumentException(
"No data configured for " + testMethod.getName());
}
@Test(dataProvider = "cases")
public void acceptsValidInput(String input) {
// Assert the valid-input behavior.
}
@Test(dataProvider = "cases")
public void rejectsInvalidInput(String input) {
// Assert the invalid-input behavior.
}
}The explicit exception makes an unhandled consumer visible instead of returning an accidental empty or inappropriate data set. Adapt the conditions and values to the cases your tests actually cover.
Run data-driven invocations in parallel
Parallel execution is opt-in on the provider: set parallel = true on @DataProvider. The TestNG documentation describes a default data-provider pool size of 10 for parallel data providers launched from an XML suite. A suite can set data-provider-thread-count to change that count; provider thread-count configuration only takes effect when parallel mode is selected.
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import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
public class ParallelLoginTest {
@DataProvider(name = "credentials", parallel = true)
public Object[][] credentials() {
return new Object[][] {
{"alice", "correct-horse"},
{"bob", "battery-staple"}
};
}
@Test(dataProvider = "credentials")
public void loginAcceptsCredentials(String username, String password) {
// Exercise the behavior under test here.
}
}<suite name="tests" data-provider-thread-count="4">
<test name="login">
<classes>
<class name="ParallelLoginTest"/>
</classes>
</test>
</suite>The value 4 is an illustrative suite setting, not a performance recommendation or measured result. Confirm the suite attributes against the DTD and TestNG version used by your project.
Pool-sharing options in TestNG 7.9.0 and later
The documentation identifies two additional controls as available starting with TestNG 7.9.0:
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share-thread-pool-for-data-providersshares a pool among data-driven tests in a suite; its size is set bydata-provider-thread-count.use-global-thread-poolshares a pool for regular and data-driven tests; its size is set bythread-count.
These settings are version-bound. Check the TestNG version and suite DTD in your project before adding them; do not assume a configuration accepted by one version applies to another.
Check for shared-state hazards
Parallelism changes the execution conditions of your tests. Before enabling it, check whether invocations write to the same account, file, database record, or mutable test fixture. Isolate test data or coordinate access where needed. The TestNG documentation describes the concurrency settings, but it cannot establish that a particular application or test suite is safe to run concurrently.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Choosing a provider layout
| Approach | Best fit | Trade-off |
|---|---|---|
| Provider in the test class | Data used by one test class or a small, local group of tests. | Easy to find beside the consumer; sharing it across unrelated classes can create duplication. |
| Provider in a separate class | Data reused across test classes. | Centralizes shared cases; the provider method specified through dataProviderClass must be static. |
| Fixed rows | A stable set of known input cases. | Simple to inspect; each row must be maintained as cases change. |
| Method-aware provider | Multiple test methods need a shared provider entry point but different data. | Can reduce duplication; the method-selection logic needs maintenance as consumers change. |
| Sequential invocations | Tests with shared state or no need for concurrent execution. | Does not require enabling data-provider parallelism. |
| Parallel invocations | Tests whose inputs and side effects are safe to execute concurrently. | Requires concurrency-safe test design and suite/version-aware pool configuration. |
Troubleshooting common DataProvider problems
- TestNG cannot find the provider: Check that the string in
dataProvidermatches the provider name. If it is in another class, setdataProviderClass; if it is in the same class or a base class, verify its placement and annotation. - Test method arguments do not match the data: Compare every returned row with the consumer’s parameters in order. Each row must supply the arguments expected by that invocation.
- External provider is not usable: When using
dataProviderClass, confirm the named method is static, as required by the documentation. - Method-aware selection returns the wrong case or no case: Inspect the method-name branches and ensure every consumer using the provider is handled. An explicit exception for unknown consumers makes omissions easier to diagnose.
- Configured provider thread count appears ignored: Confirm that parallel mode is enabled and that the suite runner and XML configuration are the ones actually being used. The documented provider thread-count setting only takes effect when parallel mode is selected.
- Suite rejects a pool-sharing setting: Check the installed TestNG version and suite DTD. The two shared/global pool controls described above are documented as starting with TestNG 7.9.0.
- Parallel tests fail inconsistently: Look for shared mutable state or test resources used by multiple invocations. Parallel configuration does not make those resources safe automatically.
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Frequently Asked Questions
Where can I check which DataProvider options my installed TestNG version supports?
Use the TestNG documentation and the suite DTD that matches the version installed in your project; the documentation page is at testng.org/documentation.html.
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