diff --git a/brush/pybrush.py b/brush/pybrush.py
index cac154c6..d0665a1c 100644
--- a/brush/pybrush.py
+++ b/brush/pybrush.py
@@ -1,11 +1,11 @@
 
-from _brush import CBrush # TODO: stop calling cbrush
+from _brush import CBrush, Dataset, SearchSpace # TODO: stop calling cbrush, rename it
 from sklearn.base import BaseEstimator, ClassifierMixin, RegressorMixin, TransformerMixin
 
 # TODO? LOGGER AND ARCHIVE
 
 # TODO: GET DOCUMENTATION BACK
-class PybrushEstimator(BaseEstimator):
+class BrushEstimator(BaseEstimator):
     def __init__(self):
         self.cbrush_ = CBrush()
 
@@ -28,12 +28,12 @@ def score(self,X,y,Z=None):
         pass
 
 
-class PybrushRegressor(PybrushEstimator):
+class BrushRegressor(BrushEstimator):
     def __init__(self,**kwargs):
         pass
 
 
-class PybrushClassifier(PybrushEstimator):
+class BrushClassifier(BrushEstimator):
     def __init__(self,**kwargs):
         pass
 
diff --git a/tests/cpp/test_evolution_step.cpp b/tests/cpp/test_evaluation.cpp
similarity index 100%
rename from tests/cpp/test_evolution_step.cpp
rename to tests/cpp/test_evaluation.cpp
diff --git a/tests/cpp/test_params.cpp b/tests/cpp/test_params.cpp
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/cpp/test_population.cpp b/tests/cpp/test_population.cpp
index 68a407ee..0f7f53d5 100644
--- a/tests/cpp/test_population.cpp
+++ b/tests/cpp/test_population.cpp
@@ -1,18 +1,143 @@
 #include "testsHeader.h"
 
+#include "../../src/individual.cpp"
+#include "../../src/population.cpp" // TODO: figure out if thats ok to include cpps instead of headers
+#include "../../src/eval/evaluation.cpp"
+#include "../../src/selection/nsga2.cpp"
+#include "../../src/selection/selection.cpp"
+
+using namespace Brush::Pop;
+using namespace Brush::Sel;
+using namespace Brush::Eval;
+
 TEST(Population, PopulationTests)
-{
+{    
+    // works with even and uneven pop sizes. (TODO: PARAMETERIZE this test to do it with even and uneven, and single individual pop)
+
+    MatrixXf X(4,2); 
+    VectorXf y(4); 
+
+    X << 0,1,  
+         0.47942554,0.87758256,  
+         0.84147098,  0.54030231,
+         0.99749499,  0.0707372;
+    y << 3.0,  3.59159876,  3.30384889,  2.20720158;
+
+    fmt::print("Initializing all classes;\n");
+    Dataset data(X,y);
+
+    SearchSpace SS;
+    SS.init(data);
 
-    Population<T> pop; 
+    Parameters params;
+    Population pop = Population<ProgramType::Regressor>(params.pop_size, params.num_islands); 
+
+    // aux classes (they are not tested in-depth in this file)
+    Evaluation evaluator = Evaluation<ProgramType::Regressor>(params.scorer_);
+    Selection selector = Selection<ProgramType::Regressor>(params.sel, false);
+    Selection survivor = Selection<ProgramType::Regressor>(params.surv, true);
+    Variation variator = Variation<ProgramType::Regressor>(params, SS);
+            
+    selector.set_operator();
+    survivor.set_operator();
+
+    // size, all individuals were initialized
+    ASSERT_TRUE(pop.size() == pop.individuals.size()
+             && pop.size() == params.pop_size);
+
+    fmt::print("Initializing individuals in the population:\n");
+    pop.init(SS, params);
+    for (auto& ind : pop.individuals)
+    {
+        fmt::print("Individual: {}\n", ind.program.get_model("compact", true));
+    }
 
-    // size,
-    // island sizes growns and comes back to the same,
-    // update and prep offspring slots.
-    // no overlap in island indexes.
-    // works with even and uneven pop sizes.
-    // initialize population works?
-    // migrate?
     // print models
+    fmt::print("Printing from population method:\n{}\n", pop.print_models());
+
+    // no overlap in island indexes
+
+    fmt::print("Testing island ranges\n");
+    for (std::size_t i = 0; i < pop.island_ranges.size() - 1; ++i) {
+        int last = std::get<1>(pop.island_ranges.at(i));
+        int next_first = std::get<0>(pop.island_ranges.at(i+1));
+
+        //(last index from one island is EQUAL than first) (no gaps between island)
+        // (this assumes that we will never iterate to the last index in for loops. TODO: make sure we dont)
+        ASSERT_TRUE(last == next_first);
+
+        // difference between island sizes is at most 1
+        auto delta = last - std::get<0>(pop.island_ranges.at(i));
+        auto next_delta = std::get<1>(pop.island_ranges.at(i+1)) - next_first;
+        ASSERT_TRUE(delta <= next_delta+1 && next_delta <= delta+1);
+    }
+
+    // island sizes increases and comes back to the same values after update
+    fmt::print("Performing all steps of an evolution\n");
+    auto original_islands = pop.island_ranges;
+    for (int i=0; i<10; ++i) // update and prep offspring slots works properly
+    {   // wax on wax off
+        
+        fmt::print("Evaluating population\n");
+        vector<vector<size_t>> island_parents;
+        island_parents.resize(pop.n_islands);
+        for (int j=0; j<pop.n_islands; ++j)
+        {
+            fmt::print("Island {}, range [{}, {}]\n", j,
+            std::get<0>(pop.get_island_range(j)), 
+            std::get<1>(pop.get_island_range(j)) );
+
+            fmt::print("Fitness\n");
+            // we can calculate the fitness for each island
+            evaluator.fitness(pop, pop.get_island_range(j), data, params, true, false);
+
+            fmt::print("Selection\n");
+            // just so we can call the update method
+            vector<size_t> parents = selector.select(pop, pop.get_island_range(j), params, data);
+            
+            ASSERT_TRUE(parents.size() > 0);
+            fmt::print("Updating parents\n");
+            island_parents.at(j) = parents;
+        }
     
+        fmt::print("Preparing offspring\n");
+        pop.prep_offspring_slots();
+        ASSERT_TRUE(pop.size() == params.pop_size*2);
+
+        fmt::print("Preparing survivors\n");
+        vector<size_t> survivors(params.pop_size);
+        for (int j=0; j<pop.n_islands; ++j)
+        {
+            fmt::print("Variations for island {}\n", j);
+            // variation applied to population
+            variator.vary(pop, pop.get_island_range(j), island_parents.at(j));
+
+            fmt::print("fitting {}\n", j);
+            evaluator.fitness(pop, pop.get_island_range(j), data, params, true, true);
+        
+            fmt::print("survivors\n", j);
+            auto island_survivors = survivor.survive(pop, pop.get_island_range(j), params, data);
+
+            fmt::print("Updating global array\n");
+            auto [idx_start, idx_end] = pop.get_island_range(j);
+            
+            for (unsigned k = 0; k<island_survivors.size(); ++k)
+            {
+                fmt::print("{}, ", k);
+                // divide by two because the islands are keeping the offspring at this step, and we want survivors to have the same size as the original pop
+                survivors.at(idx_start/2 + k) = island_survivors.at(k);
+            }
+        }
+        
+        fmt::print("Updating and migrating\n");
+        pop.update(survivors); 
+        ASSERT_TRUE(pop.size() == params.pop_size);
+
+        pop.migrate();
+        ASSERT_TRUE(pop.size() == params.pop_size);
+
+        fmt::print("Printing generation {} population:\n{}\n", i, pop.print_models());
+    }
+    ASSERT_TRUE(original_islands == pop.island_ranges);
 }
 
diff --git a/tests/cpp/testsHeader.h b/tests/cpp/testsHeader.h
index e846c2e6..47c4350d 100644
--- a/tests/cpp/testsHeader.h
+++ b/tests/cpp/testsHeader.h
@@ -33,8 +33,7 @@ using std::stof;
 #include "../../src/program/program.h"
 #include "../../src/individual.h"
 #include "../../src/search_space.h"
-#include "../../src/variation.h"
-#include "../../src/variation.cpp" // TODO: is this ok?
+#include "../../src/variation.cpp" // TODO: is this ok? (otherwise I would have to create a test separated file, or move the implementation to the header)
 
 using namespace Brush;
 using namespace Brush::Data;