Add test for graphs in history (#872)

* add test for graphs in loaded history;
* add test for `Individual` properties.

test/unit/composer/test_history.py

@@ -7,7 +7,6 @@
 import pytest
 
 from fedot.api.main import Fedot
-from fedot.core.optimisers.gp_comp.pipeline_composer_requirements import PipelineComposerRequirements
 from fedot.core.dag.graph import Graph
 from fedot.core.dag.verification_rules import DEFAULT_DAG_RULES
 from fedot.core.data.data import InputData
@@ -18,6 +17,7 @@
 from fedot.core.optimisers.gp_comp.individual import Individual, ParentOperator
 from fedot.core.optimisers.gp_comp.operators.crossover import CrossoverTypesEnum, Crossover
 from fedot.core.optimisers.gp_comp.operators.mutation import MutationTypesEnum, Mutation
+from fedot.core.optimisers.gp_comp.pipeline_composer_requirements import PipelineComposerRequirements
 from fedot.core.optimisers.objective import PipelineObjectiveEvaluate
 from fedot.core.optimisers.objective.data_source_splitter import DataSourceSplitter
 from fedot.core.optimisers.objective.objective import Objective
@@ -125,6 +125,15 @@ def test_newly_generated_history():
     loaded_history = OptHistory.load(dumped_history).save()
     assert dumped_history is not None
     assert dumped_history == loaded_history, 'The history is not equal to itself after reloading!'
+    for ind in chain(*history.individuals):
+        # All individuals in `history.individuals` must have a native generation.
+        assert ind.has_native_generation
+        if ind.native_generation == 0:
+            continue
+        # All individuals must have parents, except for the initial assumptions.
+        assert ind.parents
+        # The first of `operators_from_prev_generation` must point to `parents_from_prev_generation`.
+        assert ind.parents_from_prev_generation == list(ind.operators_from_prev_generation[0].parent_individuals)
 
 
 def assert_intermediate_metrics(pipeline: Graph):
@@ -195,8 +204,9 @@ def test_history_backward_compatibility():
     # Assert that all history pipelines have fitness
     assert len(historical_pipelines) == len(all_historical_fitness)
     assert np.shape(history.individuals) == np.shape(historical_fitness)
-    # Assert that fitness, parent_individuals, and objective are valid
+    # Assert that fitness, graph, parent_individuals, and objective are valid
     assert all(isinstance(ind.fitness, SingleObjFitness) for ind in chain(*history.individuals))
+    assert all(ind.graph.nodes for ind in chain(*history.individuals))
     assert all(isinstance(parent_ind, Individual)
                for ind in chain(*history.individuals)
                for parent_op in ind.operators_from_prev_generation