With first parameter present

No. Code ((Nihongo)) ((Nihongo/sandbox))
1 ((Nihongo|Japan)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
2 ((Nihongo|Japan|日本)) Japan (日本) Japan (日本)
3 ((Nihongo|Japan||Nippon)) Japan (Nippon) Japan (Nippon)
4 ((Nihongo|Japan|日本|Nippon)) Japan (日本, Nippon) Japan (日本, Nippon)
5 ((Nihongo|Japan|日本|Nippon|Extra)) Japan (日本, Nippon, Extra) Japan (日本, Nippon, Extra)
6 ((Nihongo|Japan|日本|Nippon|Extra|Extra2)) Japan (日本, Nippon, Extra) Extra2 Japan (日本, Nippon, Extra) Extra2
7 ((Nihongo|Japan||Nippon|Extra|Extra2)) Japan (Nippon, Extra) Extra2 Japan (Nippon, Extra) Extra2
8 ((Nihongo|Japan|日本||Extra|Extra2)) Japan (日本, Extra) Extra2 Japan (日本, Extra) Extra2
9 ((Nihongo|Japan|日本||Extra)) Japan (日本, Extra) Japan (日本, Extra)
10 ((Nihongo|Japan|||Extra|Extra2)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
11 ((Nihongo|Japan||||Extra2)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)

With first parameter absent

No. Code ((Nihongo)) ((Nihongo/sandbox))
12 ((Nihongo)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
13 ((Nihongo||日本)) (日本) (日本)
14 ((Nihongo|||Nippon)) Nippon Nippon
15 ((Nihongo||日本|Nippon)) Nippon (日本) Nippon (日本)
16 ((Nihongo||日本|Nippon|Extra)) Nippon (日本, Extra) Nippon (日本, Extra)
17 ((Nihongo||日本|Nippon|Extra|Extra2)) Nippon (日本, Extra) Extra2 Nippon (日本, Extra) Extra2
18 ((Nihongo|||Nippon|Extra|Extra2)) Nippon (Extra) Extra2 Nippon (Extra) Extra2
19 ((Nihongo||日本||Extra|Extra2)) (日本, Extra) Extra2 (日本, Extra) Extra2
20 ((Nihongo||日本||Extra)) (日本, Extra) (日本, Extra)
21 ((Nihongo||||Extra|Extra2)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
22 ((Nihongo|||||Extra2)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)

With first parameter present and |lead=yes

No. Code ((Nihongo)) ((Nihongo/sandbox))
23 ((Nihongo|Japan|lead=yes)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
24 ((Nihongo|Japan|日本|lead=yes)) Japan (Japanese: 日本) Japan (Japanese: 日本)
25 ((Nihongo|Japan||Nippon|lead=yes)) Japan (Hepburn: Nippon) Japan (Hepburn: Nippon)
26 ((Nihongo|Japan|日本|Nippon|lead=yes)) Japan (Japanese: 日本, Hepburn: Nippon) Japan (Japanese: 日本, Hepburn: Nippon)
27 ((Nihongo|Japan|日本|Nippon|Extra|lead=yes)) Japan (Japanese: 日本, Hepburn: Nippon, Extra) Japan (Japanese: 日本, Hepburn: Nippon, Extra)
28 ((Nihongo|Japan|日本|Nippon|Extra|Extra2|lead=yes)) Japan (Japanese: 日本, Hepburn: Nippon, Extra) Extra2 Japan (Japanese: 日本, Hepburn: Nippon, Extra) Extra2
29 ((Nihongo|Japan||Nippon|Extra|Extra2|lead=yes)) Japan (Hepburn: Nippon, Extra) Extra2 Japan (Hepburn: Nippon, Extra) Extra2
30 ((Nihongo|Japan|日本||Extra|Extra2|lead=yes)) Japan (Japanese: 日本, Extra) Extra2 Japan (Japanese: 日本, Extra) Extra2
31 ((Nihongo|Japan|日本||Extra|lead=yes)) Japan (Japanese: 日本, Extra) Japan (Japanese: 日本, Extra)
32 ((Nihongo|Japan|||Extra|Extra2|lead=yes)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
33 ((Nihongo|Japan||||Extra2|lead=yes)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)

With first parameter absent and |lead=yes

No. Code ((Nihongo)) ((Nihongo/sandbox))
34 ((Nihongo|lead=yes)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
35 ((Nihongo||日本|lead=yes)) (Japanese: 日本) (Japanese: 日本)
36 ((Nihongo|||Nippon|lead=yes)) Nippon Nippon
37 ((Nihongo||日本|Nippon|lead=yes)) Nippon (Japanese: 日本) Nippon (Japanese: 日本)
38 ((Nihongo||日本|Nippon|Extra|lead=yes)) Nippon (Japanese: 日本, Extra) Nippon (Japanese: 日本, Extra)
39 ((Nihongo||日本|Nippon|Extra|Extra2|lead=yes)) Nippon (Japanese: 日本, Extra) Extra2 Nippon (Japanese: 日本, Extra) Extra2
40 ((Nihongo|||Nippon|Extra|Extra2|lead=yes)) Nippon (Extra) Extra2 Nippon (Extra) Extra2
41 ((Nihongo||日本||Extra|Extra2|lead=yes)) (Japanese: 日本, Extra) Extra2 (Japanese: 日本, Extra) Extra2
42 ((Nihongo||日本||Extra|lead=yes)) (Japanese: 日本, Extra) (Japanese: 日本, Extra)
43 ((Nihongo||||Extra|Extra2|lead=yes)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
44 ((Nihongo|||||Extra2|lead=yes)) error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)

Other testcases

No. Code ((Nihongo)) ((Nihongo/sandbox))
45 This ((Nihongo|should|||be|one)) line This error: ((nihongo)): Japanese or romaji text required (help) line This error: ((nihongo)): Japanese or romaji text required (help) line
46 ((Nihongo|English|日本語|Nihon|How does this look with a very long explanation|that is being continued outside of the parentheses?)) English (日本語, Nihon, How does this look with a very long explanation) that is being continued outside of the parentheses? English (日本語, Nihon, How does this look with a very long explanation) that is being continued outside of the parentheses?

With first parameter present; template wrapped in bold markup

No. Code ((Nihongo)) ((Nihongo/sandbox))
47 '''((Nihongo|Japan))''' error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
48 '''((Nihongo|Japan|日本))''' Japan (日本) Japan (日本)
49 '''((Nihongo|Japan||Nippon))''' Japan (Nippon) Japan (Nippon)
50 '''((Nihongo|Japan|日本|Nippon))''' Japan (日本, Nippon) Japan (日本, Nippon)
51 '''((Nihongo|Japan|日本|Nippon|Extra))''' Japan (日本, Nippon, Extra) Japan (日本, Nippon, Extra)
52 '''((Nihongo|Japan|日本|Nippon|Extra|Extra2))''' Japan (日本, Nippon, Extra) Extra2 Japan (日本, Nippon, Extra) Extra2
53 '''((Nihongo|Japan||Nippon|Extra|Extra2))''' Japan (Nippon, Extra) Extra2 Japan (Nippon, Extra) Extra2
54 '''((Nihongo|Japan|日本||Extra|Extra2))''' Japan (日本, Extra) Extra2 Japan (日本, Extra) Extra2
55 '''((Nihongo|Japan|日本||Extra))''' Japan (日本, Extra) Japan (日本, Extra)
56 '''((Nihongo|Japan|||Extra|Extra2))''' error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
57 '''((Nihongo|Japan||||Extra2))''' error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)

With first parameter absent; template wrapped in bold markup

No. Code ((Nihongo)) ((Nihongo/sandbox))
58 '''((Nihongo))''' error: ((nihongo)): Japanese or romaji text required (help)'''<span class="error" style="font-size:100%">error: ((nihongo)): Japanese or romaji text required ([[Template:nihongo|help]])</span>''' error: ((nihongo)): Japanese or romaji text required (help)'''<span class="error" style="font-size:100%">error: ((nihongo)): Japanese or romaji text required ([[Template:nihongo|help]])</span>'''
59 '''((Nihongo||日本))''' (日本) (日本)
60 '''((Nihongo|||Nippon))''' Nippon Nippon
61 '''((Nihongo||日本|Nippon))''' Nippon (日本) Nippon (日本)
62 '''((Nihongo||日本|Nippon|Extra))''' Nippon (日本, Extra) Nippon (日本, Extra)
63 '''((Nihongo||日本|Nippon|Extra|Extra2))''' Nippon (日本, Extra) Extra2 Nippon (日本, Extra) Extra2
64 '''((Nihongo|||Nippon|Extra|Extra2))''' Nippon (Extra) Extra2 Nippon (Extra) Extra2
65 '''((Nihongo||日本||Extra|Extra2))''' (日本, Extra) Extra2 (日本, Extra) Extra2
66 '''((Nihongo||日本||Extra))''' (日本, Extra) (日本, Extra)
67 '''((Nihongo||||Extra|Extra2))''' error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)
68 '''((Nihongo|||||Extra2))''' error: ((nihongo)): Japanese or romaji text required (help) error: ((nihongo)): Japanese or romaji text required (help)

With romaji that may cause kerning issues (just look how italics text touches the first and final bracket) ← like that.

No. Code ((Nihongo)) ((Nihongo/sandbox))
69 ((Nihongo|well, it's big||ja, ōkii)) well, it's big (ja, ōkii) well, it's big (ja, ōkii)
70 ((Nihongo|well, it's big|じゃ、じゃ、大きい|ja, ōkii)) well, it's big (じゃ、大きい, ja, ōkii) well, it's big (じゃ、大きい, ja, ōkii)
71 ((Nihongo|well, it's big|じゃ、大きい|ja, ōkii|Extra)) well, it's big (じゃ、大きい, ja, ōkii, Extra) well, it's big (じゃ、大きい, ja, ōkii, Extra)
72 ((Nihongo|well, it's big|じゃ、大きい|ja, ōkii|Extra|Extra2)) well, it's big (じゃ、大きい, ja, ōkii, Extra) Extra2 well, it's big (じゃ、大きい, ja, ōkii, Extra) Extra2
73 ((Nihongo|well, it's big||ja, ōkii|Extra|Extra2)) well, it's big (ja, ōkii, Extra) Extra2 well, it's big (ja, ōkii, Extra) Extra2