accordant-test-generation

Test Generation in Accordant

Accordant generates tests by exploring the state graph defined by your spec, then running the generated sequences against your real system.

The State Graph

Starting from an initial state, Accordant applies each input to compute resulting states, then recurses. This builds a graph where:

• Nodes = States the system can be in
• Edges = Operations that transition between states

Generating Tests

Basic Usage

var spec = CreateSpec();
var initialState = new BankState();

// Define inputs to explore
var inputs = new InputSet
{
    spec.GetOperation<string, ApiResult<decimal>>("CreateAccount").With("alice", "Create alice"),
    spec.GetOperation<(string, decimal), ApiResult<decimal>>("Deposit").With(("alice", 100m), "Deposit 100"),
    spec.GetOperation<(string, decimal), ApiResult<decimal>>("Withdraw").With(("alice", 30m), "Withdraw 30"),
    spec.GetOperation<(string, decimal), ApiResult<decimal>>("Withdraw").With(("alice", 200m), "Withdraw 200 (overdraft)"),
    spec.GetOperation<string, ApiResult<decimal>>("DeleteAccount").With("alice", "Delete alice"),
};

// Generate test cases
var testCases = spec.GenerateTests(initialState, inputs, new TestGenerationOptions
{
    MaxDepth = 5
});

TestGenerationOptions

Option	Description	Default
MaxDepth	Maximum sequence length	5
StateConstraint	Prune states during exploration	None
MaxConcurrencyLevel	For concurrent test generation	3
SequentialTestCaseAlgorithm	How paths are extracted	StateCoverage

Constraining the State Space

Prevent state explosion with StateConstraint:

var options = new TestGenerationOptions
{
    MaxDepth = 5,
    StateConstraint = state =>
    {
        var s = (BankState)state;
        // Limit: max 2 accounts, balances under 500
        return s.Accounts.Count <= 2 && 
               s.Accounts.Values.All(b => b <= 500);
    }
};

Test Case Algorithms