test: issue 451

Author: avik-pal

test/misc/issues_tests.jl

@@ -0,0 +1,22 @@
+@testitem "Issue #451" tags=[:misc] begin
+    f(u, p) = u^2 - p
+
+    jac_calls = 0
+    function df(u, p)
+        global jac_calls += 1
+        return 2u
+    end
+
+    fn = NonlinearFunction(f; jac = df)
+    prob = NonlinearProblem(fn, 1.0, 2.0)
+    sol = solve(prob, NewtonRaphson())
+    @test sol.retcode == ReturnCode.Success
+    @test jac_calls ≥ 1
+
+    jac_calls = 0
+    fn2 = NonlinearFunction(f)
+    prob = NonlinearProblem(fn2, 1.0, 2.0)
+    sol = solve(prob, NewtonRaphson())
+    @test sol.retcode == ReturnCode.Success
+    @test jac_calls == 0
+end