Add missing file

Author: gaurav-arya

test/update_coeffs_testutils.jl

@@ -0,0 +1,28 @@
+# Utilities for testing update coefficient behaviour with state-dependent (i.e. dependent on u/p/t) functions
+
+mutable struct WrapFunc{F,U,P,T}
+    func::F
+    u::U
+    p::P
+    t::T
+end
+
+(w::WrapFunc)(u) = sum(w.u) * w.p * w.t * w.func(u) 
+function (w::WrapFunc)(v, u) 
+    w.func(v, u)
+    lmul!(sum(w.u) * w.p * w.t, v)
+end
+
+update_coefficients(w::WrapFunc, u, p, t) = WrapFunc(w.func, u, p, t)
+function update_coefficients!(w::WrapFunc, u, p, t)
+    w.u = u
+    w.p = p
+    w.t = t
+end
+
+# Helper function for testing correct update coefficients behaviour of operators
+function update_coefficients_for_test!(L, u, p, t)
+    update_coefficients!(L, u, p, t)
+    # Force function hiding inside L to update. Should be a null-op if previous line works correctly
+    update_coefficients!(L.op.f, u, p, t) 
+end