feat(nix/runTestsuite): add assertDoesNotThrow

assertDoesNotThrow is like assertThrows, but fails if the expression
throws. In that case the new unexpected-throw branch of AssertErrorContext
is returned.

Change-Id: I7195eb5df8965456e9ab9b69e35ec96b33f00a35
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2476
Tested-by: BuildkiteCI
Reviewed-by: Profpatsch <mail@profpatsch.de>

nix/runTestsuite/default.nix

@@ -61,6 +61,7 @@ let
       should-throw = struct "should-throw" {
         expr = any;
       };
+      unexpected-throw = struct "unexpected-throw" { };
     };
 
   # The result of an assert,
@@ -119,6 +120,11 @@ let
       in
         assertBoolContext context desc (throws expr));
 
+  # assert that the expression does not throw when `deepSeq`-ed
+  assertDoesNotThrow = defun [ string any AssertResult ]
+    (desc: expr:
+      assertBoolContext { unexpected-throw = { }; } desc (!(throws expr)));
+
   # Annotate a bunch of asserts with a descriptive name
   it = desc: asserts: {
     it-desc = desc;
@@ -171,6 +177,7 @@ in {
   inherit
     assertEq
     assertThrows
+    assertDoesNotThrow
     it
     runTestsuite
     ;