The word he's is a singular contraction, not a possessive form.
The contraction he's is a shortened form of the pronoun 'he' and the verb 'is'.
The contraction he's functions as a subject and verb (or auxiliary verb) in a sentence or a clause.
The possessive form of the personal pronoun he is his.
Pronouns that function as possessives do not use an apostrophe.
Examples:
He is my brother. Or: He's my brother. (contraction)
The house on the corner is his. (possessive pronoun)
His house is on the corner. (possessive adjective)
The singular possessive form of "test" is "test's".
The singular possessive pronouns are mine, yours, his, hers, and its. The singular possessive adjectives are my, your, his, her, and its.
The singular possessive is ant's.The plural possessive is ants'.
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive of dish is dish's
Taco's is the singular possessive.
The singular possessive form is classmate's.
The singular possessive is biker's; the plural possessive is bikers'.
The singular possessive is fish's.
Buzz's is the singular possessive.
Grave's is the singular possessive.
The singular possessive is Martin's.