Print a diff for compared data #412
Description
luatest has an is_equal/is_not_equal assertions.
Currently, output for tables/multiline strings/msgpack buffers looks as the following:
code
local t = require('luatest')
local g = t.group()
g.test_table_assertion = function()
local a = {
a = {
["a"] = 1,
["b"] = 2,
["c"] = 3,
},
}
local b = {
a = {
["a"] = 1,
["b"] = 5,
["c"] = 8,
},
}
t.assert_equals(a, b, 'compare tables')
end
g.test_string_assertion = function()
local a = [[
aaaaa
bbbbb
ccccc
]]
local b = [[
aaaaa
ddddd
ccccc
]]
t.assert_equals(a, b, 'compare multiline strings')
end
g.test_msgpack_assertion = function()
local msgpack = require('msgpack')
local a = {1, 2, 3}
local b = {1, 4, 3}
t.assert_equals(msgpack.encode(a), msgpack.encode(b), 'compare encoded msgpack')
endTables:
1) app-luatest.sample.test_table_assertion
...b/sources/MRG/tarantool/test/app-luatest/sample_test.lua:21: compare tables
expected: {a = {a = 1, b = 5, c = 8}}
actual: {a = {a = 1, b = 2, c = 3}}
Multiline strings:
2) app-luatest.sample.test_string_assertion
...b/sources/MRG/tarantool/test/app-luatest/sample_test.lua:36: compare multiline strings
expected:
"aaaaa\
ddddd\
ccccc\
"
actual:
"aaaaa\
bbbbb\
ccccc\
"
msgpack:
3) app-luatest.sample.test_msgpack_assertion
...b/sources/MRG/tarantool/test/app-luatest/sample_test.lua:43: compare encoded msgpack
expected: "\1\4\3"
actual: "\1\2\3"
This output is not convenient for debugging.
I propose to print a diff for this data in case of triggered assertion. This would be much more convenient to get a difference in comparison:
String:
@@ -1,3 +1,3 @@
aaaaa
-ddddd
+bbbbb
cccccTables:
@@ -1,6 +1,6 @@
---
- a:
- b: 2
+ b: 5
a: 1
- c: 3
+ c: 8
...How it can be achieved? I propose to use a diff-match Lua module 1 for comparing strings, Tables should be serialized to YAML before comparing. Msgpack buffers should be decoded and serialized to YAML if it is a table.
See also:
- https://github.com/charlesvdv/assert_json
- https://github.com/davidpdrsn/assert-json-diff
- PyTest assertions: https://docs.pytest.org/en/7.1.x/how-to/assert.html