[Test] Switch real gas derivative tests to thermo consistency tests

Removed `getIsothermalCompressibility` and `getThermalExpansionCoeff` from `PengRobinson_Test` and `RedlichKwongMFTP_Test`.
Add finite difference tests to `TestConsistency` as `betaT_eq_minus_dmv_dP_const_T_div_mv` and `alphaV_eq_dmv_dT_const_P_div_mv`.

test/thermo/consistency.cpp

@@ -345,6 +345,56 @@ TEST_P(TestConsistency, dSdv_const_T_eq_dPdT_const_V) {
     }
 }
 
+TEST_P(TestConsistency, betaT_eq_minus_dmv_dP_const_T_div_mv)
+{
+    double betaT1;
+    try {
+        betaT1 = phase->isothermalCompressibility();
+    } catch (NotImplementedError& err) {
+        GTEST_SKIP() << err.getMethod() << " threw NotImplementedError";
+    }
+
+    double T = phase->temperature();
+    double P1 = phase->pressure();
+    double mv1 = phase->molarVolume();
+
+    double P2 = P1 * (1 + 1e-7);
+    phase->setState_TP(T, P2);
+    double betaT2 = phase->isothermalCompressibility();
+    double mv2 = phase->molarVolume();
+
+    double betaT_mid = 0.5 * (betaT1 + betaT2);
+    double mv_mid = 0.5 * (mv1 + mv2);
+    double betaT_fd = -1 / mv_mid * (mv2 - mv1) / (P2 - P1);
+
+    EXPECT_NEAR(betaT_fd, betaT_mid, max({rtol_fd * betaT_mid, rtol_fd * betaT_fd, atol}));
+}
+
+TEST_P(TestConsistency, alphaV_eq_dmv_dT_const_P_div_mv)
+{
+    double alphaV1;
+    try {
+        alphaV1 = phase->thermalExpansionCoeff();
+    } catch (NotImplementedError& err) {
+        GTEST_SKIP() << err.getMethod() << " threw NotImplementedError";
+    }
+
+    double P = phase->pressure();
+    double T1 = phase->temperature();
+    double mv1 = phase->molarVolume();
+
+    double T2 = T1 * (1 + 1e-7);
+    phase->setState_TP(T2, P);
+    double alphaV2 = phase->thermalExpansionCoeff();
+    double mv2 = phase->molarVolume();
+
+    double alphaV_mid = 0.5 * (alphaV1 + alphaV2);
+    double mv_mid = 0.5 * (mv1 + mv2);
+    double alphaV_fd = 1 / mv_mid * (mv2 - mv1) / (T2 - T1);
+
+    EXPECT_NEAR(alphaV_fd, alphaV_mid, max({rtol_fd * alphaV_mid, rtol_fd * alphaV_fd, atol}));
+}
+
 // ---------- Tests for consistency of standard state properties ---------------
 
 TEST_P(TestConsistency, hk0_eq_uk0_plus_p_vk0)