return DependentsSet.dependencyToAll("classpath data of previous compilation is incomplete");
        }
        ClassSetAnalysis.ClassSetDiff classpathChanges = currentClasspath.findChangesSince(previousClasspath);
        return previous.findDependentsOfClasspathChanges(classpathChanges);
    }

    private ClassSetAnalysis getClasspath() {

        ClassSetAnalysis s2 = snapshot(["A": TestHashCodes.hashCodeFrom(0xaa), "B": TestHashCodes.hashCodeFrom(0xbbbb)])

        expect:
        s1.findChangesSince(s2).dependents.allDependentClasses == ["B"] as Set
        s2.findChangesSince(s1).dependents.allDependentClasses == ["B", "C"] as Set
    }

    def "returns empty analysis"() {
        def a = analysis([:])

        this.compilerApiData = compilerApiData;
    }

    /**
     * Computes the types affected by the changes since some other class set, including transitively affected classes.
     */
    public ClassSetDiff findChangesSince(ClassSetAnalysis other) {
        DependentsSet directChanges = classAnalysis.getChangedClassesSince(other.classAnalysis);
        if (directChanges.isDependencyToAll()) {