[claude-opus-4.6] Add more tests for the new PBBM implementation

[Copilot]

PR #3399 introduced new PBBM model toggles (hydrodynamic model, effective diffusion, Hintz-Johnson) but only tested them in non-precipitation scenarios with 2-bin formulations. This adds coverage for the missing combinations.

New test classes (8)

• Precipitation + each model option (3 tests): Validates mass balance, precipitation occurrence, and insoluble drug monotonicity when combining precipitation with hydrodynamic OFF, effective diffusion ON, or Hintz-Johnson OFF
• All model options toggled simultaneously: Hydrodynamic OFF + effective diffusion ON + Hintz-Johnson OFF with 2 bins
• Single-bin variants: 1-bin formulations with hydrodynamic OFF and effective diffusion ON
• Effective diffusion + hydrodynamic OFF: Tests the interaction between these two diffusion-layer-related options

All tests follow the existing concern_for_SimulationWithParticlesFormulation BDD pattern:

public class when_running_particles_simulation_with_two_bins_with_precipitation_without_hydrodynamic_model 
   : concern_for_SimulationWithParticlesFormulation
{
   protected override int NumberOfBins => 2;

   protected override void SetupSimulation()
   {
      PrecipitatedDrugSoluble = false;
      UseHydrodynamicModel = false;
      Solubility(Constants.Compartment.DUODENUM).Value = 1e-12;
      _simulation.OutputSchema.Intervals.Last().EndTime.Value = 900;
   }
   // CheckMassBalance, CheckPrecipitation, CheckSumOfParticlesNumberFractionsPerBin, CheckInsolubleDrugIncreasing
}

Original prompt

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This section details on the original issue you should resolve

<issue_title>V13: more tests for the new PBBM implementation</issue_title>
<issue_description>Check which aspects of the modified oral absorption / particles dissolution model require new (integration) tests and add them</issue_description>

<agent_instructions>The changes were introduced in this PR: #3399
(the database changes are also summarized in the excel file attachments in the issue #3353 )

The changes are the implementation of the papers https://doi.org/10.1016/j.ejps.2025.107164 and https://doi.org/10.1016/j.ejps.2025.107189 and include:

• Novel and versatile model for drug release kinetics that enables bridging between various in vitro test conditions
  • Integration of micellar solubilization
  • Differentiation between the release kinetics of free and micelle-bound drug
  • Mechanistic description of the effect of medium agitation rate on the diffusion layer thickness
  • Refined kinetics for particle regrowth and precipitation
• Updated human GI tract:
  • Incorporation of physiological bile salt concentrations in the intestinal lumen
  • Addition of population variability in luminal pH across all GI tract segments
  • Description of stomach pH as a function of hydrogen dilution due to water intake
    </agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes V13: more tests for the new PBBM implementation #3406

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[Copilot]

Pull request overview

This PR adds comprehensive integration test coverage for the new PBBM (Physiologically-Based Biopharmaceutics Modeling) model options introduced in PR #3399. The original PR added three new model toggles (hydrodynamic model, effective diffusion, and Hintz-Johnson) but only tested them in non-precipitation scenarios with 2-bin formulations. These new tests fill the coverage gaps by testing precipitation scenarios, single-bin formulations, and combined model option configurations.

Changes:

• Added 7 new integration test classes covering precipitation scenarios with each model option toggle
• Added tests for combined model options (all three toggles used simultaneously)
• Added single-bin formulation tests with model option toggles
• Added test for interaction between effective diffusion and hydrodynamic model options

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