public SmithyDiffTestSuite setModelAssemblerFactory(Supplier<ModelAssembler> modelAssemblerFactory) {
        this.modelAssemblerFactory = Objects.requireNonNull(modelAssemblerFactory);
        return this;
    }
Sets a custom {@link ModelAssembler} factory to use to create a
{@code ModelAssembler} for each test case.

<p>The supplier must return a new instance of a Model assembler
each time it is called. Model assemblers are mutated and execute
in parallel.

@param modelAssemblerFactory Model assembler factory to use.
@return Returns the test suite.
smithy-diff/src/main/java/software/amazon/smithy/diff/testrunner/SmithyDiffTestSuite.java