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Edit File: FinjectiveTest.m2

TEST /// --Fedder's original F-injective not F-pure, deformation examples
    S = ZZ/2[x,y,z,u,v];
    I =  minors(2, matrix {{x^2, z, v}, {u, z, y^2}});
    J = I + ideal(x,y);
    assert(isFInjective(S/I));
    assert(isFInjective(S/J));
    assert(isFPure(S/J));
    assert(not isFPure(S/I));
///

TEST /// --cone over P1 times supersingular elliptic curve (non CM)
    S = ZZ/3[xs, ys, zs, xt, yt, zt];
    EP1 = ZZ/3[x,y,z,s,t]/ideal(x^3+y^2*z-x*z^2); --supersingular elliptic curve
    f = map(EP1, S, {x*s, y*s, z*s, x*t, y*t, z*t});
    R = S/(ker f);
    assert(not isFInjective(R));
///

TEST /// --cone over P1 times ordinary elliptic curve (non CM)
    S = ZZ/3[xs, ys, zs, xt, yt, zt];
    EP1 = ZZ/3[x,y,z,s,t]/ideal(y^2*z-x^3+x*y*z); --ordinary elliptic curve
    f = map(EP1, S, {x*s, y*s, z*s, x*t, y*t, z*t});
    R = S/(ker f);
    assert( isFInjective(R) );
///

TEST /// --FPureModule cone over ordinary elliptic curve
    R = ZZ/7[x,y,z]/ideal(x^3+y^3+z^3);
    HSLmod = FPureModule(CurrentRing => R);
    assert(HSLmod#0 == HSLmod#1);
///

TEST /// --the isLocal option
    R = ZZ/5[x,y,z]/ideal((x-2)^3 + y^3 + z^3); --supersingular
    assert( isFInjective(R, AtOrigin=>true) );
    assert( not isFInjective(R) );
///

TEST /// --FPureModule cone over supersingular elliptic curve
    R = ZZ/5[x,y,z]/ideal(x^3+y^3+z^3);
    HSLmod = FPureModule(CurrentRing => R);
    assert(not (HSLmod#0 == HSLmod#1));
///

TEST /// --FPureModule of an F-pure pair
    R = ZZ/7[x,y]
    HSLmod = FPureModule(5/6, y^2-x^3);
    assert((HSLmod#0 == HSLmod#1));
///

TEST /// --isFInjective of a ring with no variables
    R = ZZ/17[];
    assert(isFInjective(R));
///

TEST /// --checking brute force F-injective vs canonicalStrategy
    R = ZZ/3[x,y,z]/ideal(y^2*z-x^3+x*y*z); --ordinary
    assert(isFInjective(R));
    assert(isFInjective(R, CanonicalStrategy=>null));
    S = ZZ/3[x,y,z]/ideal(x^3+y^2*z-x*z^2); --supersingular
    assert(not isFInjective(S));
    assert(not isFInjective(S, CanonicalStrategy=>null));
///

TEST /// --checking FPureModule vs descendIdeal #1
    R = ZZ/7[x,y];
    maxIdeal = ideal(x,y);
    unitIdeal = ideal(sub(1,R));
    f = x*y*(x+y);
    unit = sub(1, R);
    assert((FPureModule(2/3, f, CanonicalIdeal => maxIdeal, GeneratorList => {unit}))#0 == maxIdeal );
    assert((FPureModule(2/3, f, CanonicalIdeal => unitIdeal, GeneratorList => {unit}))#0 == unitIdeal );
    assert((descendIdeal(1, {4}, {f}, maxIdeal))#0 == maxIdeal);
    assert((descendIdeal(1, {4}, {f}, unitIdeal))#0 == unitIdeal);
    assert((FPureModule(37/48, f, CanonicalIdeal => unitIdeal, GeneratorList => {unit}))#0 == maxIdeal);
    assert((FPureModule(37/48, f, CanonicalIdeal => unitIdeal, GeneratorList => {unit}))#0 == maxIdeal);
///