test(refactor): Add Toxiproxy Hspec test infrastructure

Author: mkleczek

nix/tools/tests.nix

@@ -42,7 +42,8 @@ let
       }
       ''
         ${withTools.withPg} -f test/observability/fixtures/load.sql \
-          ${cabal-install}/bin/cabal v2-run ${devCabalOptions} test:observability -- "''${_arg_leftovers[@]}"
+          ${withTools.withToxiproxyPg} \
+            ${cabal-install}/bin/cabal v2-run ${devCabalOptions} test:observability -- "''${_arg_leftovers[@]}"
       '';
 
   testDoctests =

postgrest.cabal

@@ -203,6 +203,21 @@ executable postgrest
   else
     ghc-options: -O2
 
+library test-utils
+  visibility:         private
+  default-language:   Haskell2010
+  default-extensions: OverloadedStrings
+                      NoImplicitPrelude
+  hs-source-dirs:     test/lib
+  exposed-modules:    Toxiproxy
+  build-depends:      base              >= 4.9 && < 4.22
+                    , aeson             >= 2.0.3 && < 2.3
+                    , containers        >= 0.5.7 && < 0.8
+                    , http-client       >= 0.7.19 && < 0.8
+                    , servant-client    >= 0.20.3.0 && < 0.21
+                    , servant           >= 0.20.3.0 && < 0.21
+                    , text              >= 1.2.2 && < 2.2
+
 test-suite spec
   type:               exitcode-stdio-1.0
   default-language:   Haskell2010
@@ -311,6 +326,7 @@ test-suite observability
                       Observation.JwtCache
                       Observation.MetricsSpec
                       Observation.SchemaCacheSpec
+                      Observation.ToxiSpec
   build-depends:      base              >= 4.9 && < 4.22
                     , base64-bytestring >= 1 && < 1.3
                     , bytestring        >= 0.10.8 && < 0.13
@@ -322,11 +338,15 @@ test-suite observability
                     , hspec-wai-json    >= 0.10 && < 0.12
                     , http-types        >= 0.12.3 && < 0.13
                     , jose-jwt          >= 0.9.6 && < 0.11
+                    , monad-control     >= 1.0.1 && < 1.1
                     , postgrest
                     , prometheus-client >= 1.1.1 && < 1.2.0
                     , protolude         >= 0.3.1 && < 0.4
                     , text              >= 1.2.2 && < 2.2
+                    , test-utils
+                    , transformers-base >= 0.4.4 && < 0.5
                     , wai               >= 3.2.1 && < 3.3
+                    , wai-extra         >= 3.1.8 && < 3.2
   ghc-options:        -threaded -O0 -Werror -Wall -fwarn-identities
                       -fno-spec-constr -optP-Wno-nonportable-include-path
                       -fwrite-ide-info

src/PostgREST/AppState.hs

@@ -6,6 +6,7 @@
 module PostgREST.AppState
   ( AppState
   , destroy
+  , flushPool
   , getConfig
   , getSchemaCache
   , getMainThreadId