Nullable Strategy¶

Controls whether nullable types produce null or a concrete value during fixture generation.

The default is NullableStrategy.NullOnCircularReference, which prefers concrete values and only returns null when a nullable type would otherwise create a circular reference.

Variants¶

NullOnCircularReference¶

Produces concrete values for nullable types unless resolving the value would create a circular reference.

some { nullableStrategy = NullableStrategy.NullOnCircularReference }

This is the default strategy.

data class Node(val next: Node?)

val node = some<Node>()

node.next // null

The nullable circular field is resolved as null, so generation stops instead of recursing forever. Non-nullable circular references still throw SomeCircularReferenceException because no finite value can satisfy them:

data class StrictNode(val next: StrictNode)

some<StrictNode>() // throws SomeCircularReferenceException

AlwaysNull¶

Always produces null for nullable types.

some { nullableStrategy = NullableStrategy.AlwaysNull }

Use this strategy when testing edge cases or validating null-handling logic.

NeverNull¶

Always produces a non-null concrete value for nullable types.

some { nullableStrategy = NullableStrategy.NeverNull }

Use this strategy when you want to ensure all nullable fields are populated, which is useful for testing the "happy path" scenarios.

Random¶

Produces null based on a configurable probability.

// 50% chance of null (default)
some { nullableStrategy = NullableStrategy.Random() }

// 20% chance of null (mostly non-null values)
some { nullableStrategy = NullableStrategy.Random(probability = 0.2) }

// 80% chance of null (mostly null values)
some { nullableStrategy = NullableStrategy.Random(probability = 0.8) }

// Never generate null (0% chance) - equivalent to NeverNull
some { nullableStrategy = NullableStrategy.Random(probability = 0.0) }

// Always generate null (100% chance) - equivalent to AlwaysNull
some { nullableStrategy = NullableStrategy.Random(probability = 1.0) }

Probability parameter¶

The default probability is 0.5, giving an equal chance of null or non-null values.

Summary table¶