test: fix thermal piston test

Author: AayushSabharwal

test/Thermal/piston.jl

@@ -42,6 +42,6 @@ using ModelingToolkitStandardLibrary.Blocks
     # The initial value doesn't add up to absolute zero, while the rest do. To avoid
     # tolerance on the latter, the test is split in two parts.
     @test sol[piston.gas.Q_flow][1] + sol[piston.coolant.Q_flow][1]≈0 atol=1e-6
-    @test sol[piston.gas.Q_flow][2:end] + sol[piston.coolant.Q_flow][2:end] ==
-          zeros(length(sol) - 1)
+    @test sol[piston.gas.Q_flow][2:end] + sol[piston.coolant.Q_flow][2:end] ≈
+          zeros(length(sol) - 1) atol = 1e-6
 end