diff --git a/packages/conferer/conferer.cabal b/packages/conferer/conferer.cabal
index 96e881c..a3c051e 100644
--- a/packages/conferer/conferer.cabal
+++ b/packages/conferer/conferer.cabal
@@ -73,6 +73,7 @@ test-suite specs
   main-is: ConfererSpecMain.hs
   other-modules:
       Conferer.ConfigSpec
+      Conferer.ExceptionMessagesSpec
       Conferer.FromConfig.BoolSpec
       Conferer.FromConfig.Extended
       Conferer.FromConfig.FileSpec
@@ -83,13 +84,16 @@ test-suite specs
       Conferer.FromConfigSpec
       Conferer.GenericsSpec
       Conferer.KeySpec
+      Conferer.MultiSourceErrorsSpec
       Conferer.Source.CLIArgsSpec
       Conferer.Source.EnvSpec
+      Conferer.Source.ExplanationsSpec
       Conferer.Source.InMemorySpec
       Conferer.Source.NamespacedSpec
       Conferer.Source.NullSpec
       Conferer.Source.PropertiesFileSpec
       ConfererSpec
+      Tests
       Paths_conferer
   hs-source-dirs:
       test
@@ -101,6 +105,8 @@ test-suite specs
       RecordWildCards
       StrictData
   ghc-options: -Wall -Wredundant-constraints -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -main-is ConfererSpecMain
+  build-tool-depends:
+      hspec-discover:hspec-discover
   build-depends:
       QuickCheck
     , base >=4.3 && <5
@@ -111,6 +117,9 @@ test-suite specs
     , directory >=1.2 && <2.0
     , filepath >=1.0 && <2.0
     , hspec
+    , hspec-core
+    , hspec-golden
+    , template-haskell
     , text >=1.1 && <2.2
   default-language: Haskell2010
   if impl(ghc >= 8.4.1)
diff --git a/packages/conferer/package.yaml b/packages/conferer/package.yaml
index a27019e..5291ffa 100644
--- a/packages/conferer/package.yaml
+++ b/packages/conferer/package.yaml
@@ -21,9 +21,13 @@ tests:
   specs:
     main: ConfererSpecMain
     source-dirs: test
+    build-tools:
+      - hspec-discover
     dependencies:
       - conferer
       - hspec
+      - hspec-core
+      - hspec-golden
+      - template-haskell
       - deepseq
       - QuickCheck
-
diff --git a/packages/conferer/src/Conferer/FromConfig/Internal/Types.hs b/packages/conferer/src/Conferer/FromConfig/Internal/Types.hs
index 4c74fde..007dd10 100644
--- a/packages/conferer/src/Conferer/FromConfig/Internal/Types.hs
+++ b/packages/conferer/src/Conferer/FromConfig/Internal/Types.hs
@@ -14,6 +14,7 @@ module Conferer.FromConfig.Internal.Types where
 import Control.Exception
 import Conferer.Key (Key)
 import Data.Text (Text)
+import qualified Data.Text as Text
 import Data.Typeable
 import Conferer.Config.Internal.Types
 import Conferer.Source.Internal
@@ -28,11 +29,13 @@ data ConfigParsingError =
 type OriginalValue = Text
 
 instance Exception ConfigParsingError where
-  displayException (ConfigParsingError key _value aTypeRep sourceIndex c) =
+  displayException (ConfigParsingError key value aTypeRep sourceIndex c) =
     concat
     [ "Failed to interpret "
     , explainSettedKey (configSources c !! sourceIndex) key
-    , " as '"
+    , " with a value of '"
+    , Text.unpack value
+    , "' as '"
     , show aTypeRep
     , "'"
     ]
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Bool parsing error from CLI args/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Bool parsing error from CLI args/golden
new file mode 100644
index 0000000..21ade9f
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Bool parsing error from CLI args/golden	
@@ -0,0 +1,2 @@
+Failed to interpret cli param '--enabled' with a value of 'maybe' as 'Bool'
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Int parsing error from env source/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Int parsing error from env source/golden
new file mode 100644
index 0000000..b9dbb17
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Int parsing error from env source/golden	
@@ -0,0 +1,2 @@
+Failed to interpret env var 'APP_PORT' with a value of 'not_a_number' as 'Int'
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Int parsing error from properties file/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Int parsing error from properties file/golden
new file mode 100644
index 0000000..97d5d84
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/ConfigParsingError exception messages/formats Int parsing error from properties file/golden	
@@ -0,0 +1,2 @@
+Failed to interpret key 'timeout' (on file '/tmp/test.properties') with a value of 'invalid' as 'Int'
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats missing key with complex type/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats missing key with complex type/golden
new file mode 100644
index 0000000..655791c
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats missing key with complex type/golden	
@@ -0,0 +1,6 @@
+Couldn't find a '[Char]'.
+
+You can set it by either:
+* Setting the environment variable: APP_ALLOWED_HOSTS_KEYS
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from CLI source/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from CLI source/golden
new file mode 100644
index 0000000..db3d2e9
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from CLI source/golden	
@@ -0,0 +1,6 @@
+Couldn't find a 'Int'.
+
+You can set it by either:
+* Passing the cli arg: --server.port="the value"
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from env source/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from env source/golden
new file mode 100644
index 0000000..d654fb8
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from env source/golden	
@@ -0,0 +1,6 @@
+Couldn't find a '[Char]'.
+
+You can set it by either:
+* Setting the environment variable: APP_DATABASE_HOST
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from multiple sources/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from multiple sources/golden
new file mode 100644
index 0000000..eae08ff
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from multiple sources/golden	
@@ -0,0 +1,8 @@
+Couldn't find a 'Int'.
+
+You can set it by either:
+* Setting the environment variable: APP_CACHE_TTL
+* Passing the cli arg: --cache.ttl="the value"
+* Adding a new line 'cache.ttl=some value' to the file '/etc/app.properties'
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from non-existent properties file/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from non-existent properties file/golden
new file mode 100644
index 0000000..5ee7033
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from non-existent properties file/golden	
@@ -0,0 +1,6 @@
+Couldn't find a '[Char]'.
+
+You can set it by either:
+* Creating a file '/path/to/missing.properties' (it doesn't exist now) and adding a line 'redis.host=some value'.
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from properties file/golden b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from properties file/golden
new file mode 100644
index 0000000..98de90b
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.golden/MissingRequiredKey exception messages/formats single key missing from properties file/golden	
@@ -0,0 +1,6 @@
+Couldn't find a '[Char]'.
+
+You can set it by either:
+* Adding a new line 'api.key=some value' to the file '/etc/app.properties'
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/ExceptionMessagesSpec.hs b/packages/conferer/test/Conferer/ExceptionMessagesSpec.hs
new file mode 100644
index 0000000..f391022
--- /dev/null
+++ b/packages/conferer/test/Conferer/ExceptionMessagesSpec.hs
@@ -0,0 +1,93 @@
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE RecordWildCards #-}
+{-# LANGUAGE TemplateHaskell #-}
+module Conferer.ExceptionMessagesSpec where
+
+import Test.Hspec
+import Test.Hspec.Golden
+import Control.Exception
+import Data.Text (Text)
+import qualified Data.Text as Text
+import Data.Typeable
+
+import Conferer
+import Conferer.Config
+import Conferer.FromConfig
+import Conferer.Source
+import Conferer.Source.Env (fromEnvList)
+import Conferer.Source.CLIArgs (fromArgs)
+import Conferer.Source.PropertiesFile (fromFileContent)
+import Conferer.Source.Null (NullSource(..))
+import Tests
+
+spec :: Spec
+spec = do
+  describe "ConfigParsingError exception messages" $ do
+    $(betterGolden) "formats Int parsing error from env source" $ do
+      config <- mkConfigWithEnv [("APP_PORT", "not_a_number")]
+      captureException $ fetchFromConfig @Int "port" config
+
+    $(betterGolden) "formats Bool parsing error from CLI args" $ do
+      config <- mkConfigWithCLI ["--enabled=maybe"]
+      captureException $ fetchFromConfig @Bool "enabled" config
+
+    $(betterGolden) "formats Int parsing error from properties file" $ do
+      config <- mkConfigWithProperties "/tmp/test.properties" "timeout=invalid"
+      captureException $ fetchFromConfig @Int "timeout" config
+
+  describe "MissingRequiredKey exception messages" $ do
+    $(betterGolden) "formats single key missing from env source" $ do
+      config <- mkConfigWithEnv []
+      captureException $ fetchFromConfig @String "database.host" config
+
+    $(betterGolden) "formats single key missing from CLI source" $ do
+      config <- mkConfigWithCLI []
+      captureException $ fetchFromConfig @Int "server.port" config
+
+    $(betterGolden) "formats single key missing from properties file" $ do
+      config <- mkConfigWithProperties "/etc/app.properties" ""
+      captureException $ fetchFromConfig @String "api.key" config
+
+    $(betterGolden) "formats single key missing from non-existent properties file" $ do
+      config <- mkConfigWithNonExistentProperties "/path/to/missing.properties"
+      captureException $ fetchFromConfig @String "redis.host" config
+
+    $(betterGolden) "formats single key missing from multiple sources" $ do
+      config <- mkConfigWithMultipleSources
+      captureException $ fetchFromConfig @Int "cache.ttl" config
+
+    $(betterGolden) "formats missing key with complex type" $ do
+      config <- mkConfigWithEnv []
+      captureException $ fetchFromConfig @[String] "allowed.hosts" config
+
+mkConfigWithEnv :: [(String, String)] -> IO Config
+mkConfigWithEnv envVars =
+  addSource (\_ -> return $ fromEnvList envVars "APP") emptyConfig
+
+mkConfigWithCLI :: [String] -> IO Config
+mkConfigWithCLI args =
+  addSource (\_ -> return $ fromArgs args) emptyConfig
+
+mkConfigWithProperties :: FilePath -> Text -> IO Config
+mkConfigWithProperties path content =
+  addSource (\_ -> return $ fromFileContent path content) emptyConfig
+
+mkConfigWithNonExistentProperties :: FilePath -> IO Config
+mkConfigWithNonExistentProperties path = do
+  -- Use Null source with a custom explanation that simulates non-existent file
+  let mkSource = \_ -> return $ Source $ NullSource $ \key ->
+        concat
+        [ "Creating a file '"
+        , path
+        , "' (it doesn't exist now) and adding a line '"
+        , Text.unpack $ Text.intercalate "." $ rawKeyComponents key
+        , "=some value'."
+        ]
+  addSource mkSource emptyConfig
+
+mkConfigWithMultipleSources :: IO Config
+mkConfigWithMultipleSources = do
+  config1 <- addSource (\_ -> return $ fromEnvList [] "APP") emptyConfig
+  config2 <- addSource (\_ -> return $ fromArgs []) config1
+  addSource (\_ -> return $ fromFileContent "/etc/app.properties" "") config2
diff --git a/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows all sources for missing nested key/golden b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows all sources for missing nested key/golden
new file mode 100644
index 0000000..a5bd525
--- /dev/null
+++ b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows all sources for missing nested key/golden	
@@ -0,0 +1,8 @@
+Couldn't find a 'Int'.
+
+You can set it by either:
+* Setting the environment variable: APP_APP_WORKER_THREADS
+* Passing the cli arg: --app.worker.threads="the value"
+* Adding a new line 'app.worker.threads=some value' to the file '/etc/myapp.properties'
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows all sources when key is missing from env + CLI + properties/golden b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows all sources when key is missing from env + CLI + properties/golden
new file mode 100644
index 0000000..86a8cd7
--- /dev/null
+++ b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows all sources when key is missing from env + CLI + properties/golden	
@@ -0,0 +1,8 @@
+Couldn't find a '[Char]'.
+
+You can set it by either:
+* Setting the environment variable: APP_DATABASE_PASSWORD
+* Passing the cli arg: --database.password="the value"
+* Adding a new line 'database.password=some value' to the file '/etc/myapp.properties'
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows combined env, CLI, and in-memory sources/golden b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows combined env, CLI, and in-memory sources/golden
new file mode 100644
index 0000000..0df6247
--- /dev/null
+++ b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows combined env, CLI, and in-memory sources/golden	
@@ -0,0 +1,9 @@
+Couldn't find a '[Char]'.
+
+You can set it by either:
+* Setting the environment variable: APP_ALLOWED_ORIGINS_KEYS
+* Passing the cli arg: --allowed.origins.keys="the value"
+* Adding a new line 'allowed.origins.keys=some value' to the file '/etc/myapp.properties'
+* Setting key '"allowed.origins.keys"' in the config
+
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows correct source when parsing fails in second source/golden b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows correct source when parsing fails in second source/golden
new file mode 100644
index 0000000..23e3402
--- /dev/null
+++ b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows correct source when parsing fails in second source/golden	
@@ -0,0 +1,2 @@
+Failed to interpret cli param '--server.port' with a value of 'not-a-number' as 'Int'
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows parsing error with correct source index from properties file/golden b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows parsing error with correct source index from properties file/golden
new file mode 100644
index 0000000..8017911
--- /dev/null
+++ b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.golden/Multi-source error messages/shows parsing error with correct source index from properties file/golden	
@@ -0,0 +1,2 @@
+Failed to interpret key 'feature.enabled' (on file '/config/app.properties') with a value of 'maybe' as 'Bool'
+HasCallStack backtrace
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/MultiSourceErrorsSpec.hs b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.hs
new file mode 100644
index 0000000..f360ae6
--- /dev/null
+++ b/packages/conferer/test/Conferer/MultiSourceErrorsSpec.hs
@@ -0,0 +1,72 @@
+{-# LANGUAGE TypeApplications #-}
+{-# LANGUAGE TemplateHaskell #-}
+module Conferer.MultiSourceErrorsSpec where
+
+import Test.Hspec
+import Test.Hspec.Golden
+import Control.Exception
+import Data.Text (Text)
+import qualified Data.Text as Text
+
+import Conferer
+import Conferer.Config
+import Conferer.Source.Env (fromEnvList)
+import Conferer.Source.CLIArgs (fromArgs)
+import Conferer.Source.PropertiesFile (fromFileContent)
+import Conferer.Source.InMemory (fromAssociations, ExplainNotFound (..), ExplainSettedKey (..))
+import Tests
+
+spec :: Spec
+spec = do
+  describe "Multi-source error messages" $ do
+    $(betterGolden) "shows all sources when key is missing from env + CLI + properties" $ do
+      putStrLn "lelle"
+      config <- mkConfigTripleSource
+      captureException $ fetchFromConfig @String "database.password" config
+
+    $(betterGolden) "shows correct source when parsing fails in second source" $ do
+      config <- mkConfigWithInvalidValueInCLI
+      captureException $ fetchFromConfig @Int "server.port" config
+
+    $(betterGolden) "shows all sources for missing nested key" $ do
+      config <- mkConfigTripleSource
+      captureException $ fetchFromConfig @Int "app.worker.threads" config
+
+    $(betterGolden) "shows combined env, CLI, and in-memory sources" $ do
+      config <- mkConfigQuadSource
+      captureException $ fetchFromConfig @[String] "allowed.origins" config
+
+    $(betterGolden) "shows parsing error with correct source index from properties file" $ do
+      config <- mkConfigWithInvalidValueInProperties
+      captureException $ fetchFromConfig @Bool "feature.enabled" config
+
+-- Helper functions
+
+mkConfigTripleSource :: IO Config
+mkConfigTripleSource = do
+  pure emptyConfig
+    >>= addSource (\_ -> return $ fromEnvList [] "APP")
+    >>= addSource (\_ -> return $ fromArgs [])
+    >>= addSource (\_ -> return $ fromFileContent "/etc/myapp.properties" "")
+
+mkConfigQuadSource :: IO Config
+mkConfigQuadSource = do
+  -- InMemory source needs explanation functions
+  let explainNotF = ExplainNotFound $ \k -> "Setting key '" ++ show k ++ "' in the config"
+      explainSetF = ExplainSettedKey $ \k -> "key '" ++ show k ++ "' from config"
+  pure emptyConfig
+    >>= addSource (\_ -> return $ fromEnvList [] "APP")
+    >>= addSource (\_ -> return $ fromArgs [])
+    >>= addSource (\_ -> return $ fromFileContent "/etc/myapp.properties" "")
+    >>= addSource (\_ -> return $ fromAssociations explainNotF explainSetF [])
+
+mkConfigWithInvalidValueInCLI :: IO Config
+mkConfigWithInvalidValueInCLI = do
+  config1 <- addSource (\_ -> return $ fromEnvList [] "APP") emptyConfig
+  addSource (\_ -> return $ fromArgs ["--server.port=not-a-number"]) config1
+
+mkConfigWithInvalidValueInProperties :: IO Config
+mkConfigWithInvalidValueInProperties = do
+  config1 <- addSource (\_ -> return $ fromEnvList [] "APP") emptyConfig
+  config2 <- addSource (\_ -> return $ fromArgs []) config1
+  addSource (\_ -> return $ fromFileContent "/config/app.properties" "feature.enabled=maybe") config2
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in CLIArgsSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in CLIArgsSource/golden
new file mode 100644
index 0000000..a35f4b3
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in CLIArgsSource/golden	
@@ -0,0 +1 @@
+cli param '--server.port'
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in EnvSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in EnvSource/golden
new file mode 100644
index 0000000..e2ca92d
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in EnvSource/golden	
@@ -0,0 +1 @@
+env var 'APP_DATABASE_HOST'
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in NamespacedSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in NamespacedSource/golden
new file mode 100644
index 0000000..615f23b
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in NamespacedSource/golden	
@@ -0,0 +1 @@
+Doing nothing, you can't use this source for that key
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in PropertiesFileSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in PropertiesFileSource/golden
new file mode 100644
index 0000000..97d416c
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found key in PropertiesFileSource/golden	
@@ -0,0 +1 @@
+key 'api.key' (on file '/etc/app.properties')
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found nested key in EnvSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found nested key in EnvSource/golden
new file mode 100644
index 0000000..caf5280
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains a found nested key in EnvSource/golden	
@@ -0,0 +1 @@
+env var 'APP_SERVER_SSL_ENABLED'
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in CLIArgsSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in CLIArgsSource/golden
new file mode 100644
index 0000000..aea16ea
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in CLIArgsSource/golden	
@@ -0,0 +1 @@
+Passing the cli arg: --server.port="the value"
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in EnvSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in EnvSource/golden
new file mode 100644
index 0000000..95b1a2a
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in EnvSource/golden	
@@ -0,0 +1 @@
+Setting the environment variable: APP_DATABASE_HOST
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in NamespacedSource wrapping Env/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in NamespacedSource wrapping Env/golden
new file mode 100644
index 0000000..615f23b
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in NamespacedSource wrapping Env/golden	
@@ -0,0 +1 @@
+Doing nothing, you can't use this source for that key
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in PropertiesFileSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in PropertiesFileSource/golden
new file mode 100644
index 0000000..9ff6b5f
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in PropertiesFileSource/golden	
@@ -0,0 +1 @@
+Adding a new line 'api.key=some value' to the file '/etc/app.properties'
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in non-existent PropertiesFileSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in non-existent PropertiesFileSource/golden
new file mode 100644
index 0000000..6b29869
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a key in non-existent PropertiesFileSource/golden	
@@ -0,0 +1 @@
+IMPOSSIBLE
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a nested key in CLIArgsSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a nested key in CLIArgsSource/golden
new file mode 100644
index 0000000..9389d4e
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a nested key in CLIArgsSource/golden	
@@ -0,0 +1 @@
+Passing the cli arg: --database.connection.timeout="the value"
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a nested key in EnvSource/golden b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a nested key in EnvSource/golden
new file mode 100644
index 0000000..8f37703
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.golden/Source explainNotFound/explains how to set a nested key in EnvSource/golden	
@@ -0,0 +1 @@
+Setting the environment variable: MYAPP_SERVER_SSL_ENABLED
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/ExplanationsSpec.hs b/packages/conferer/test/Conferer/Source/ExplanationsSpec.hs
new file mode 100644
index 0000000..da638cf
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/ExplanationsSpec.hs
@@ -0,0 +1,78 @@
+{-# LANGUAGE BlockArguments #-}
+{-# LANGUAGE TemplateHaskell #-}
+module Conferer.Source.ExplanationsSpec where
+
+import Test.Hspec
+import Test.Hspec.Golden
+import qualified Data.Text as Text
+
+import Conferer.Source
+import Tests
+import Conferer.Source.Env (fromEnvList)
+import Conferer.Source.CLIArgs (fromArgs)
+import Conferer.Source.PropertiesFile (fromFileContent)
+import Conferer.Source.Namespaced (fromInner)
+import Conferer.Source.Null (NullSource(..))
+
+spec :: Spec
+spec = do
+  describe "Source explainNotFound" $ do
+    $(betterGolden) "explains how to set a key in EnvSource" $ do
+      let source = fromEnvList [] "APP"
+          explanation = explainNotFound source "database.host"
+      pure explanation
+
+    $(betterGolden)  "explains how to set a nested key in EnvSource" $ do
+      let source = fromEnvList [] "MYAPP"
+          explanation = explainNotFound source "server.ssl.enabled"
+      pure explanation
+
+    $(betterGolden) "explains how to set a key in CLIArgsSource" $ do
+      let source = fromArgs []
+          explanation = explainNotFound source "server.port"
+      pure explanation
+
+    $(betterGolden) "explains how to set a nested key in CLIArgsSource" $ do
+      let source = fromArgs []
+          explanation = explainNotFound source "database.connection.timeout"
+      pure explanation
+
+    $(betterGolden) "explains how to set a key in PropertiesFileSource" $ do
+      let source = fromFileContent "/etc/app.properties" ""
+      pure $ explainNotFound source "api.key"
+
+    $(betterGolden) "explains how to set a key in non-existent PropertiesFileSource" $ do
+      let source = Source $ NullSource $ const "IMPOSSIBLE"
+      pure $ explainNotFound source "redis.host"
+
+    $(betterGolden) "explains how to set a key in NamespacedSource wrapping Env" $ do
+      let envSource = fromEnvList [] "APP"
+          source = fromInner "worker" envSource
+          explanation = explainNotFound source "queue.name"
+      pure explanation
+
+    $(betterGolden) "explains a found key in EnvSource" $ do
+      let source = fromEnvList [("APP_DATABASE_HOST", "localhost")] "APP"
+          explanation = explainSettedKey source "database.host"
+      pure explanation
+
+    $(betterGolden) "explains a found key in CLIArgsSource" $ do
+      let source = fromArgs ["--server.port=8080"]
+          explanation = explainSettedKey source "server.port"
+      pure explanation
+
+    $(betterGolden) "explains a found key in PropertiesFileSource" $ do
+      let source = fromFileContent "/etc/app.properties" "api.key=secret123"
+          explanation = explainSettedKey source "api.key"
+      pure explanation
+
+    $(betterGolden) "explains a found nested key in EnvSource" $ do
+      let source = fromEnvList [("APP_SERVER_SSL_ENABLED", "true")] "APP"
+          explanation = explainSettedKey source "server.ssl.enabled"
+      pure explanation
+
+    $(betterGolden) "explains a found key in NamespacedSource" $ do
+      let envSource = fromEnvList [("APP_WORKER_QUEUE_NAME", "jobs")] "APP"
+          source = fromInner "worker" envSource
+          explanation = explainSettedKey source "queue.name"
+      pure explanation
diff --git a/packages/conferer/test/Conferer/Source/PropertiesFileSpec.golden/with a properties file config/#explainNotFound/recommends adding the right line to the file/golden b/packages/conferer/test/Conferer/Source/PropertiesFileSpec.golden/with a properties file config/#explainNotFound/recommends adding the right line to the file/golden
new file mode 100644
index 0000000..2c39164
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/PropertiesFileSpec.golden/with a properties file config/#explainNotFound/recommends adding the right line to the file/golden	
@@ -0,0 +1 @@
+Adding a new line 'some.key=some value' to the file 'file.properties'
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/PropertiesFileSpec.golden/with a properties file config/#explainSettedKey/recommends adding the right line to the file/golden b/packages/conferer/test/Conferer/Source/PropertiesFileSpec.golden/with a properties file config/#explainSettedKey/recommends adding the right line to the file/golden
new file mode 100644
index 0000000..5743815
--- /dev/null
+++ b/packages/conferer/test/Conferer/Source/PropertiesFileSpec.golden/with a properties file config/#explainSettedKey/recommends adding the right line to the file/golden	
@@ -0,0 +1 @@
+key 'some.key' (on file 'file.properties')
\ No newline at end of file
diff --git a/packages/conferer/test/Conferer/Source/PropertiesFileSpec.hs b/packages/conferer/test/Conferer/Source/PropertiesFileSpec.hs
index ab55718..c31e370 100644
--- a/packages/conferer/test/Conferer/Source/PropertiesFileSpec.hs
+++ b/packages/conferer/test/Conferer/Source/PropertiesFileSpec.hs
@@ -40,4 +40,3 @@ spec = do
         s <- mk "some.key=thing"
         explainSettedKey s "some.key"
           `shouldBe` "key 'some.key' (on file 'file.properties')"
-
diff --git a/packages/conferer/test/Tests.hs b/packages/conferer/test/Tests.hs
new file mode 100644
index 0000000..d9c767e
--- /dev/null
+++ b/packages/conferer/test/Tests.hs
@@ -0,0 +1,79 @@
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeApplications #-}
+module Tests where
+
+import Test.Hspec
+import Test.Hspec.Golden
+import Test.Hspec.Core.Spec
+
+import Language.Haskell.TH
+import Language.Haskell.TH.Syntax
+import Data.List (intercalate)
+import System.FilePath ((</>), dropExtension)
+import System.Directory (removeFile)
+import Control.Monad (when)
+import Control.Exception
+import qualified Data.Text as Text
+
+-- | Get the absolute path of the current module's source file
+getCurrentModulePath :: Q Exp
+getCurrentModulePath = do
+  loc <- qLocation
+  let path = loc_filename loc
+  [| path |]
+
+
+golden2
+  :: HasCallStack
+  => Bool       -- ^ Should override old value
+  -> FilePath   -- ^ Path of current file
+  -> String     -- ^ Test description
+  -> IO String  -- ^ Content (@return content@ for pure functions)
+  -> Spec
+golden2 shouldOverride sourceFilePath description runAction = do
+  pathBasedOnHspec <- intercalate "/" <$> drop 1 <$> (++ [description]) <$> getSpecDescriptionPath
+  it description $ do
+    result <- runAction
+    let pathBasedOnCurrentFile = dropExtension sourceFilePath ++ ".golden"
+    let path = pathBasedOnCurrentFile </> pathBasedOnHspec
+    let goldenPath = path </> "golden"
+    let actualPath = path </> "actual"
+
+    when shouldOverride $ removeFile goldenPath
+
+    pure $ Golden
+      { output = result
+      , encodePretty = show
+      , writeToFile = writeFile
+      , readFromFile = readFile
+      , goldenFile = goldenPath
+      , actualFile = Just actualPath
+      , failFirstTime = False
+    }
+
+betterGoldenOverride :: Q Exp
+betterGoldenOverride = do
+  loc <- qLocation
+  let path = loc_filename loc
+  [| golden2 True path |]
+
+betterGolden :: Q Exp
+betterGolden = do
+  loc <- qLocation
+  let path = (++ ".golden") $ dropExtension $ loc_filename loc
+  [| golden2 False path |]
+
+
+-- Helper functions
+
+captureException :: IO a -> IO String
+captureException action = do
+  result <- try @SomeException action
+  case result of
+    Left e -> return $
+      Text.unpack $
+      fst $
+      Text.breakOnEnd "HasCallStack backtrace" $
+      Text.pack $
+      displayException e
+    Right _ -> fail "Expected an exception but got a successful result"