diff --git a/extra/yaml/yaml-tests.factor b/extra/yaml/yaml-tests.factor
index bb1a401c29..41e1c1ba9b 100644
--- a/extra/yaml/yaml-tests.factor
+++ b/extra/yaml/yaml-tests.factor
@@ -64,3 +64,372 @@ CONSTANT: test-objs { "a" { "b" "c" } H{ { "d" "e" } } }
 ${ test-objs } [ $ test-docs yaml-docs> ] unit-test
 ${ test-docs } [ $ test-objs >yaml-docs ] unit-test
 ${ test-docs } [ $ test-docs yaml-docs> >yaml-docs ] unit-test
+
+! Lifted from pyyaml
+! http://pyyaml.org/browser/pyyaml/trunk/tests/data
+
+! !!!!!!!!!!!!!!!
+! construct-bool
+! TODO this is yaml 1.1, test it once a correct system
+! for switching between 1.2 and 1.1 is available
+! CONSTANT: construct-bool-obj H{
+!     { "canonical" t }
+!     { "answer" f }
+!     { "logical" t }
+!     { "option" t }
+!     { "but" H{ { "y" "is a string" } { "n" "is a string" } } }
+! }
+! 
+! CONSTANT: construct-bool-str """canonical: yes
+! answer: NO
+! logical: True
+! option: on
+! 
+! 
+! but:
+!     y: is a string
+!     n: is a string
+! """
+! 
+! ${ construct-bool-obj } [ $ construct-bool-str yaml> ] unit-test
+! ${ construct-bool-obj } [ $ construct-bool-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-int
+! TODO _ in numbers is yaml 1.1, test it once a correct system
+! for switching between 1.2 and 1.1 is available
+! CONSTANT: construct-int-obj H{
+!     { "canonical" 685230 }
+!     { "decimal" 685230 }
+!     { "octal" 685230 }
+!     { "hexadecimal" 685230 }
+!     { "binary" 685230 }
+!     { "sexagesimal" 685230 }
+! }
+! CONSTANT: construct-int-str """canonical: 685230
+! decimal: +685_230
+! octal: 02472256
+! hexadecimal: 0x_0A_74_AE
+! binary: 0b1010_0111_0100_1010_1110
+! sexagesimal: 190:20:30
+! """
+! 
+! ${ construct-int-obj } [ $ construct-int-str yaml> ] unit-test
+! ${ construct-int-obj } [ $ construct-int-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-map
+CONSTANT: construct-map-obj H{ {
+      "Block style"
+      H{ { "Clark" "Evans" } { "Brian" "Ingerson" } { "Oren" "Ben-Kiki" } }
+    } {
+      "Flow style"
+      H{ { "Clark" "Evans" } { "Brian" "Ingerson" } { "Oren" "Ben-Kiki" } }
+    }
+}
+
+CONSTANT: construct-map-str """# Unordered set of key: value pairs.
+Block style: !!map
+  Clark : Evans
+  Brian : Ingerson
+  Oren  : Ben-Kiki
+Flow style: !!map { Clark: Evans, Brian: Ingerson, Oren: Ben-Kiki }
+"""
+
+${ construct-map-obj } [ $ construct-map-str yaml> ] unit-test
+${ construct-map-obj } [ $ construct-map-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-null
+CONSTANT: construct-null-obj {
+    f
+    H{
+        { "empty" f }
+        { "canonical" f }
+        { "english" f }
+        { f "null key" }
+    } H{
+        {
+          "sparse"
+          { f "2nd entry" f "4th entry" f }
+        }
+    }
+}
+
+
+CONSTANT: construct-null-str """# A document may be null.
+---
+---
+# This mapping has four keys,
+# one has a value.
+empty:
+canonical: ~
+english: null
+~: null key
+---
+# This sequence has five
+# entries, two have values.
+sparse:
+  - ~
+  - 2nd entry
+  -
+  - 4th entry
+  - Null
+"""
+
+${ construct-null-obj } [ $ construct-null-str yaml-docs> ] unit-test
+! TODO Decide what to do with null -> f -> false
+! ${ construct-null-obj } [ $ construct-null-obj >yaml-docs yaml-docs> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-seq
+CONSTANT: construct-seq-obj H{
+    { "Block style" { "Mercury" "Venus" "Earth" "Mars" "Jupiter" "Saturn" "Uranus" "Neptune" "Pluto" } }
+    { "Flow style" { "Mercury" "Venus" "Earth" "Mars" "Jupiter" "Saturn" "Uranus" "Neptune" "Pluto" } }
+}
+
+CONSTANT: construct-seq-str """# Ordered sequence of nodes
+Block style: !!seq
+- Mercury   # Rotates - no light/dark sides.
+- Venus     # Deadliest. Aptly named.
+- Earth     # Mostly dirt.
+- Mars      # Seems empty.
+- Jupiter   # The king.
+- Saturn    # Pretty.
+- Uranus    # Where the sun hardly shines.
+- Neptune   # Boring. No rings.
+- Pluto     # You call this a planet?
+Flow style: !!seq [ Mercury, Venus, Earth, Mars,      # Rocks
+                    Jupiter, Saturn, Uranus, Neptune, # Gas
+                    Pluto ]                           # Overrated
+"""
+
+${ construct-seq-obj } [ $ construct-seq-str yaml> ] unit-test
+${ construct-seq-obj } [ $ construct-seq-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-set
+! TODO implement this to hash-set
+! CONSTANT: construct-set-obj H{
+!   {
+!    "baseball players" HS{
+!       "Mark McGwire"
+!       "Sammy Sosa"
+!       "Ken Griffey"
+!     }
+!   } {
+!     "baseball teams" HS{
+!       "Boston Red Sox"
+!       "Detroit Tigers"
+!       "New York Yankees"
+!     }
+!   }
+! }
+! 
+! CONSTANT: construct-set-str """# Explicitly typed set.
+! baseball players: !!set
+!   ? Mark McGwire
+!   ? Sammy Sosa
+!   ? Ken Griffey
+! # Flow style
+! baseball teams: !!set { Boston Red Sox, Detroit Tigers, New York Yankees }
+! """
+! 
+! ${ construct-set-obj } [ $ construct-set-str yaml> ] unit-test
+! ${ construct-set-obj } [ $ construct-set-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-binary
+
+! # byte-arrays contents generate by the following python script
+! # which uses the string from pyyaml tests
+! from __future__ import print_function
+! l=0
+! for char in "GIF89a\x0c\x00\x0c\x00\x84\x00\x00\xff\xff\xf7\xf5\xf5\xee\xe9\xe9\xe5fff\x00\x00\x00\xe7\xe7\xe7^^^\xf3\xf3\xed\x8e\x8e\x8e\xe0\xe0\xe0\x9f\x9f\x9f\x93\x93\x93\xa7\xa7\xa7\x9e\x9e\x9eiiiccc\xa3\xa3\xa3\x84\x84\x84\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9\xff\xfe\xf9!\xfe\x0eMade with GIMP\x00,\x00\x00\x00\x00\x0c\x00\x0c\x00\x00\x05,  \x8e\x810\x9e\xe3@\x14\xe8i\x10\xc4\xd1\x8a\x08\x1c\xcf\x80M$z\xef\xff0\x85p\xb8\xb01f\r\x1b\xce\x01\xc3\x01\x1e\x10' \x82\n\x01\x00;":
+!     s = str(ord(char))
+!     print(s, end='')
+!     l=l+len(s)+1
+!     if (l >= 60):
+!         print("\n", end='')
+!         l = 0
+!     else:
+!         print(' ', end='')
+! print("\n", end='')
+CONSTANT: construct-binary-obj H{
+  {
+   "canonical" B{
+      71 73 70 56 57 97 12 0 12 0 132 0 0 255 255 247 245 245 238
+      233 233 229 102 102 102 0 0 0 231 231 231 94 94 94 243 243 237
+      142 142 142 224 224 224 159 159 159 147 147 147 167 167 167
+      158 158 158 105 105 105 99 99 99 163 163 163 132 132 132 255
+      254 249 255 254 249 255 254 249 255 254 249 255 254 249 255
+      254 249 255 254 249 255 254 249 255 254 249 255 254 249 255
+      254 249 255 254 249 255 254 249 255 254 249 33 254 14 77 97
+      100 101 32 119 105 116 104 32 71 73 77 80 0 44 0 0 0 0 12 0
+      12 0 0 5 44 32 32 142 129 48 158 227 64 20 232 105 16 196 209
+      138 8 28 207 128 77 36 122 239 255 48 133 112 184 176 49 102
+      13 27 206 1 195 1 30 16 39 32 130 10 1 0 59
+    }
+  } {
+   "generic" B{
+      71 73 70 56 57 97 12 0 12 0 132 0 0 255 255 247 245 245 238
+      233 233 229 102 102 102 0 0 0 231 231 231 94 94 94 243 243 237
+      142 142 142 224 224 224 159 159 159 147 147 147 167 167 167
+      158 158 158 105 105 105 99 99 99 163 163 163 132 132 132 255
+      254 249 255 254 249 255 254 249 255 254 249 255 254 249 255
+      254 249 255 254 249 255 254 249 255 254 249 255 254 249 255
+      254 249 255 254 249 255 254 249 255 254 249 33 254 14 77 97
+      100 101 32 119 105 116 104 32 71 73 77 80 0 44 0 0 0 0 12 0
+      12 0 0 5 44 32 32 142 129 48 158 227 64 20 232 105 16 196 209
+      138 8 28 207 128 77 36 122 239 255 48 133 112 184 176 49 102
+      13 27 206 1 195 1 30 16 39 32 130 10 1 0 59
+    }
+  } {
+    "description" "The binary value above is a tiny arrow encoded as a gif image."
+  }
+}
+
+CONSTANT: construct-binary-str """canonical: !!binary "\\
+ R0lGODlhDAAMAIQAAP//9/X17unp5WZmZgAAAOfn515eXvPz7Y6OjuDg4J+fn5\\
+ OTk6enp56enmlpaWNjY6Ojo4SEhP/++f/++f/++f/++f/++f/++f/++f/++f/+\\
+ +f/++f/++f/++f/++f/++SH+Dk1hZGUgd2l0aCBHSU1QACwAAAAADAAMAAAFLC\\
+ AgjoEwnuNAFOhpEMTRiggcz4BNJHrv/zCFcLiwMWYNG84BwwEeECcgggoBADs="
+generic: !!binary |
+ R0lGODlhDAAMAIQAAP//9/X17unp5WZmZgAAAOfn515eXvPz7Y6OjuDg4J+fn5
+ OTk6enp56enmlpaWNjY6Ojo4SEhP/++f/++f/++f/++f/++f/++f/++f/++f/+
+ +f/++f/++f/++f/++f/++SH+Dk1hZGUgd2l0aCBHSU1QACwAAAAADAAMAAAFLC
+ AgjoEwnuNAFOhpEMTRiggcz4BNJHrv/zCFcLiwMWYNG84BwwEeECcgggoBADs=
+description:
+ The binary value above is a tiny arrow encoded as a gif image.
+"""
+
+${ construct-binary-obj } [ $ construct-binary-str yaml> ] unit-test
+${ construct-binary-obj } [ $ construct-binary-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-merge
+! TODO decide when to merge
+! CONSTANT: construct-merge-obj {
+!     H{ { "x" 1 } { "y" 2 } }
+!     H{ { "x" 0 } { "y" 2 } }
+!     H{ { "r" 10 } }
+!     H{ { "r" 1 } }
+!     H{ { "x" 1 } { "y" 2 } { "r" 10 } { "label" "center/big" } }
+!     H{ { "x" 1 } { "y" 2 } { "r" 10 } { "label" "center/big" } }
+!     H{ { "x" 1 } { "y" 2 } { "r" 10 } { "label" "center/big" } }
+!     H{ { "x" 1 } { "y" 2 } { "r" 10 } { "label" "center/big" } }
+! }
+! 
+! CONSTANT: construct-merge-str """---
+! - &CENTER { x: 1, 'y': 2 }
+! - &LEFT { x: 0, 'y': 2 }
+! - &BIG { r: 10 }
+! - &SMALL { r: 1 }
+! 
+! # All the following maps are equal:
+! 
+! - # Explicit keys
+!   x: 1
+!   'y': 2
+!   r: 10
+!   label: center/big
+! 
+! - # Merge one map
+!   << : *CENTER
+!   r: 10
+!   label: center/big
+! 
+! - # Merge multiple maps
+!   << : [ *CENTER, *BIG ]
+!   label: center/big
+! 
+! - # Override
+!   << : [ *BIG, *LEFT, *SMALL ]
+!   x: 1
+!   label: center/big
+! """
+! 
+! ${ construct-merge-obj } [ $ construct-merge-str yaml> ] unit-test
+! ${ construct-merge-obj } [ $ construct-merge-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-omap
+! TODO what to do with omap ?
+! CONSTANT: construct-omap-obj f
+! 
+! CONSTANT: construct-omap-str """# Explicitly typed ordered map (dictionary).
+! Bestiary: !!omap
+!   - aardvark: African pig-like ant eater. Ugly.
+!   - anteater: South-American ant eater. Two species.
+!   - anaconda: South-American constrictor snake. Scaly.
+!   # Etc.
+! # Flow style
+! Numbers: !!omap [ one: 1, two: 2, three : 3 ]
+! """
+! 
+! ${ construct-omap-obj } [ $ construct-omap-str yaml> ] unit-test
+! ${ construct-omap-obj } [ $ construct-omap-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-pairs
+! TODO what to do with pairs ?
+! CONSTANT: construct-pairs-obj f
+! 
+! CONSTANT: construct-pairs-str """# Explicitly typed pairs.
+! Block tasks: !!pairs
+!   - meeting: with team.
+!   - meeting: with boss.
+!   - break: lunch.
+!   - meeting: with client.
+! Flow tasks: !!pairs [ meeting: with team, meeting: with boss ]
+! """
+! 
+! ${ construct-pairs-obj } [ $ construct-pairs-str yaml> ] unit-test
+! ${ construct-pairs-obj } [ $ construct-pairs-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-timestamp
+! TODO what to do with timestamp ?
+! CONSTANT: construct-timestamp-obj f
+! 
+! CONSTANT: construct-timestamp-str """canonical:        2001-12-15T02:59:43.1Z
+! valid iso8601:    2001-12-14t21:59:43.10-05:00
+! space separated:  2001-12-14 21:59:43.10 -5
+! no time zone (Z): 2001-12-15 2:59:43.10
+! date (00:00:00Z): 2002-12-14
+! """
+! 
+! ${ construct-timestamp-obj } [ $ construct-timestamp-str yaml> ] unit-test
+! ${ construct-timestamp-obj } [ $ construct-timestamp-obj >yaml yaml> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! construct-value
+! TODO: find something better to do with '=' ? see http://yaml.org/type/value.html
+! Maybe a global parameter to replace all maps with their default values ? See pyyaml SafeConstructor
+CONSTANT: construct-value-obj {
+    H{ { "link with" { "library1.dll" "library2.dll" } } }
+    H{ {
+        "link with" {
+            H{ { "=" "library1.dll" } { "version" 1.2 } }
+            H{ { "=" "library2.dll" } { "version" 2.3 } }
+        }
+    } }
+}
+
+CONSTANT: construct-value-str """---     # Old schema
+link with:
+  - library1.dll
+  - library2.dll
+---     # New schema
+link with:
+  - = : library1.dll
+    version: 1.2
+  - = : library2.dll
+    version: 2.3
+"""
+
+${ construct-value-obj } [ $ construct-value-str yaml-docs> ] unit-test
+${ construct-value-obj } [ $ construct-value-obj >yaml-docs yaml-docs> ] unit-test
+
+! !!!!!!!!!!!!!!!
+! *.detect